<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:01a0fcd9-755b-7813-aa52-3d2f3a78260a,g:76a784d8-5acf-499b-a9a1-a2ea11f7d9c1-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.cardinal.com/role/CondensedConsolidatedStatementofShareholdersEquity" xlink:type="simple" xlink:href="cah-20260930.xsd#CondensedConsolidatedStatementofShareholdersEquity"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/CondensedConsolidatedStatementofShareholdersEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_01a0fcd9-76c4-7e1d-8c70-85edf9c7f203" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_01a0fcd9-7611-7a68-a8c1-1966e52da514" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_01a0fcd9-76c4-7e1d-8c70-85edf9c7f203" xlink:to="loc_us-gaap_StatementTable_01a0fcd9-7611-7a68-a8c1-1966e52da514" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_01a0fcd9-7611-73dd-bce7-cba3417cad91" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_01a0fcd9-7611-7a68-a8c1-1966e52da514" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_01a0fcd9-7611-73dd-bce7-cba3417cad91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_01a0fcd9-7611-73dd-bce7-cba3417cad91_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_01a0fcd9-7611-73dd-bce7-cba3417cad91" xlink:to="loc_us-gaap_EquityComponentDomain_01a0fcd9-7611-73dd-bce7-cba3417cad91_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_01a0fcd9-7611-7dba-abde-40ba478fe842" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_01a0fcd9-7611-73dd-bce7-cba3417cad91" xlink:to="loc_us-gaap_EquityComponentDomain_01a0fcd9-7611-7dba-abde-40ba478fe842" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_01a0fcd9-7611-7076-b42e-69a8eabbdfd6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a0fcd9-7611-7dba-abde-40ba478fe842" xlink:to="loc_us-gaap_CommonStockMember_01a0fcd9-7611-7076-b42e-69a8eabbdfd6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_01a0fcd9-7611-790a-8645-bcf6063f2a31" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a0fcd9-7611-7dba-abde-40ba478fe842" xlink:to="loc_us-gaap_RetainedEarningsMember_01a0fcd9-7611-790a-8645-bcf6063f2a31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_01a0fcd9-76c4-7489-ace4-ecadfef5f5f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a0fcd9-7611-7dba-abde-40ba478fe842" xlink:to="loc_us-gaap_TreasuryStockCommonMember_01a0fcd9-76c4-7489-ace4-ecadfef5f5f4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_01a0fcd9-76c4-7855-aeb4-49e8f2b8fd70" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a0fcd9-7611-7dba-abde-40ba478fe842" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_01a0fcd9-76c4-7855-aeb4-49e8f2b8fd70" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_01a0fcd9-76c4-7e9f-b519-d90ef76c9467" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a0fcd9-7611-7dba-abde-40ba478fe842" xlink:to="loc_us-gaap_NoncontrollingInterestMember_01a0fcd9-76c4-7e9f-b519-d90ef76c9467" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_SpecialtyAllianceMember_01a182e5-0cf0-79a2-a9f0-71f74a82ba56" xlink:href="cah-20260930.xsd#cah_SpecialtyAllianceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a0fcd9-7611-7dba-abde-40ba478fe842" xlink:to="loc_cah_SpecialtyAllianceMember_01a182e5-0cf0-79a2-a9f0-71f74a82ba56" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementAxis_01a0fcd9-76c4-7d11-8fbb-b7c368ce87fd" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RestatementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_01a0fcd9-7611-7a68-a8c1-1966e52da514" xlink:to="loc_srt_RestatementAxis_01a0fcd9-76c4-7d11-8fbb-b7c368ce87fd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_01a0fcd9-76c4-7d11-8fbb-b7c368ce87fd_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_01a0fcd9-76c4-7d11-8fbb-b7c368ce87fd" xlink:to="loc_srt_RestatementDomain_01a0fcd9-76c4-7d11-8fbb-b7c368ce87fd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_01a0fcd9-76c4-7ebf-a520-b309673bd821" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_01a0fcd9-76c4-7d11-8fbb-b7c368ce87fd" xlink:to="loc_srt_RestatementDomain_01a0fcd9-76c4-7ebf-a520-b309673bd821" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_01a0fcd9-76c4-7e1d-8c70-85edf9c7f203" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_01a0fcd9-76c4-79b4-8b5d-3f6e03b30c72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_CommonStockSharesIssued_01a0fcd9-76c4-79b4-8b5d-3f6e03b30c72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_01a0fcd9-76c4-706e-bfbd-9a1d7075ebf9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_01a0fcd9-76c4-706e-bfbd-9a1d7075ebf9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_01a0fcd9-76c4-723d-8475-8a4325dfa83b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_TreasuryStockCommonShares_01a0fcd9-76c4-723d-8475-8a4325dfa83b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValue_01a0fcd9-76c4-7c43-8126-94881bc66400" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_TreasuryStockValue_01a0fcd9-76c4-7c43-8126-94881bc66400" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_01a0fcd9-76c4-76d2-b244-39457eb7d580" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_NetIncomeLoss_01a0fcd9-76c4-76d2-b244-39457eb7d580" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_01a0fcd9-76c4-79ff-a303-71b708756ae3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_ProfitLoss_01a0fcd9-76c4-79ff-a303-71b708756ae3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_01a0fcd9-76c4-73a0-84fb-db7820777115" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_01a0fcd9-76c4-73a0-84fb-db7820777115" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromRedemptions_01a0fcd9-76c4-7320-bd70-05ade6e5ca33" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestDecreaseFromRedemptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromRedemptions_01a0fcd9-76c4-7320-bd70-05ade6e5ca33" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_01a0fcd9-76c4-7426-9200-ec1291b058a2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_01a0fcd9-76c4-7426-9200-ec1291b058a2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_01a0fcd9-76c4-7e5d-97a6-0c635a2b840a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_01a0fcd9-76c4-7e5d-97a6-0c635a2b840a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_01a0fcd9-76c4-7e68-85b7-6530dbe34571" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_01a0fcd9-76c4-7e68-85b7-6530dbe34571" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_01a0fcd9-76c4-7a52-b937-687a11af961a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_01a0fcd9-76c4-7a52-b937-687a11af961a" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_01a0fcd9-76c4-77f1-81b8-8005cb890b41" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_01a0fcd9-76c4-77f1-81b8-8005cb890b41" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Dividends_01a0fcd9-76c4-7c84-b9bc-610a79721bb3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Dividends"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_Dividends_01a0fcd9-76c4-7c84-b9bc-610a79721bb3" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToMinorityShareholders_01a0fcd9-76c4-7048-a166-0bc0c4998b3d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToMinorityShareholders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_PaymentsToMinorityShareholders_01a0fcd9-76c4-7048-a166-0bc0c4998b3d" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityOther_01a0fcd9-76c4-7730-80c4-9a3347c2a144" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0fcd9-76c4-7c19-ba62-f280a17f4a66" xlink:to="loc_us-gaap_StockholdersEquityOther_01a0fcd9-76c4-7730-80c4-9a3347c2a144" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_01a0fcd9-76c4-7c05-8d41-753b68299125" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_01a0fcd9-76c4-748e-bc86-f866991f76c4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_01a0fcd9-76c4-7930-a832-5c21b6e495fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValue_01a0fcd9-76c4-7c65-8596-5c90dbdc454d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/BasisofPresentationandSummaryofSignificantAccountingPoliciesNarrativeDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#BasisofPresentationandSummaryofSignificantAccountingPoliciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/BasisofPresentationandSummaryofSignificantAccountingPoliciesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityLineItems_01a0fcd9-76c5-796b-a0df-8686992cca4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_01a0fcd9-76c5-7b69-a7c8-150da5a2aa72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_01a0fcd9-76c5-796b-a0df-8686992cca4e" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_01a0fcd9-76c5-7b69-a7c8-150da5a2aa72" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_01a0fcd9-76c5-7db9-83e9-3ffc388205af" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_01a0fcd9-76c5-7b69-a7c8-150da5a2aa72" xlink:to="loc_srt_ConsolidatedEntitiesAxis_01a0fcd9-76c5-7db9-83e9-3ffc388205af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_01a0fcd9-76c5-7db9-83e9-3ffc388205af_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_01a0fcd9-76c5-7db9-83e9-3ffc388205af" xlink:to="loc_srt_ConsolidatedEntitiesDomain_01a0fcd9-76c5-7db9-83e9-3ffc388205af_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_01a0fcd9-76c5-74db-90dc-eead7ac756ea" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_01a0fcd9-76c5-7db9-83e9-3ffc388205af" xlink:to="loc_srt_ConsolidatedEntitiesDomain_01a0fcd9-76c5-74db-90dc-eead7ac756ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_01a0fcd9-76c5-7ebc-aa80-2381535246fb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_01a0fcd9-76c5-74db-90dc-eead7ac756ea" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_01a0fcd9-76c5-7ebc-aa80-2381535246fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_01a0fcd9-76c5-734d-b03d-642124cbcc79" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_01a0fcd9-76c5-796b-a0df-8686992cca4e" xlink:to="loc_us-gaap_Liabilities_01a0fcd9-76c5-734d-b03d-642124cbcc79" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_01a0fcd9-76c5-712e-bd10-03dc2925576a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_01a0fcd9-76c5-796b-a0df-8686992cca4e" xlink:to="loc_us-gaap_Assets_01a0fcd9-76c5-712e-bd10-03dc2925576a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/AcquisitionsDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#AcquisitionsDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/AcquisitionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a0fcd9-76c5-7b00-a87f-0492b3473599" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a0fcd9-76c5-7b00-a87f-0492b3473599" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_01a0fcd9-76c5-7562-a083-6a6d665ee995" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a0fcd9-76c5-7b00-a87f-0492b3473599" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_01a0fcd9-76c5-7562-a083-6a6d665ee995" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a0fcd9-76c5-7562-a083-6a6d665ee995_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_01a0fcd9-76c5-7562-a083-6a6d665ee995" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a0fcd9-76c5-7562-a083-6a6d665ee995_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a0fcd9-76c5-7dd9-87f4-93492045245e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_01a0fcd9-76c5-7562-a083-6a6d665ee995" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a0fcd9-76c5-7dd9-87f4-93492045245e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_SolarisHealthMember_01a0fcd9-76c5-7a94-bf4c-5e333a7d9a5f" xlink:href="cah-20260930.xsd#cah_SolarisHealthMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a0fcd9-76c5-7dd9-87f4-93492045245e" xlink:to="loc_cah_SolarisHealthMember_01a0fcd9-76c5-7a94-bf4c-5e333a7d9a5f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_01a0fcd9-76c5-7730-ba33-f1f1c0e8e3d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a0fcd9-76c5-7b00-a87f-0492b3473599" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_01a0fcd9-76c5-7730-ba33-f1f1c0e8e3d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7730-ba33-f1f1c0e8e3d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_01a0fcd9-76c5-7730-ba33-f1f1c0e8e3d4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7730-ba33-f1f1c0e8e3d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7202-a1ab-acad38c44a12" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_01a0fcd9-76c5-7730-ba33-f1f1c0e8e3d4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7202-a1ab-acad38c44a12" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_01a0fcd9-76c5-7923-9564-072f32dd5fa0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CustomerRelatedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7202-a1ab-acad38c44a12" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_01a0fcd9-76c5-7923-9564-072f32dd5fa0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_TrademarksAndPatentsMember_01a0fcd9-76c5-78bb-aea9-acffe3045a91" xlink:href="cah-20260930.xsd#cah_TrademarksAndPatentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7202-a1ab-acad38c44a12" xlink:to="loc_cah_TrademarksAndPatentsMember_01a0fcd9-76c5-78bb-aea9-acffe3045a91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_01a0fcd9-76c5-70e2-97f8-a96a6d719aaf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncompeteAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7202-a1ab-acad38c44a12" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_01a0fcd9-76c5-70e2-97f8-a96a6d719aaf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_01a0fcd9-76c5-7fb0-b4ed-c43b973f6984" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a0fcd9-76c5-7b00-a87f-0492b3473599" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_01a0fcd9-76c5-7fb0-b4ed-c43b973f6984" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_01a0fcd9-76c5-7fb0-b4ed-c43b973f6984_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_01a0fcd9-76c5-7fb0-b4ed-c43b973f6984" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_01a0fcd9-76c5-7fb0-b4ed-c43b973f6984_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_01a0fcd9-76c5-7b3c-8831-6caa78326f3a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_01a0fcd9-76c5-7fb0-b4ed-c43b973f6984" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_01a0fcd9-76c5-7b3c-8831-6caa78326f3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember_01a0fcd9-76c5-7a7d-a3a8-31224f1bdce2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputDiscountRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_01a0fcd9-76c5-7b3c-8831-6caa78326f3a" xlink:to="loc_us-gaap_MeasurementInputDiscountRateMember_01a0fcd9-76c5-7a7d-a3a8-31224f1bdce2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueAxis_01a0fcd9-76c5-7030-a641-4e4a7dde6ee2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a0fcd9-76c5-7b00-a87f-0492b3473599" xlink:to="loc_us-gaap_ValuationTechniqueAxis_01a0fcd9-76c5-7030-a641-4e4a7dde6ee2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain_01a0fcd9-76c5-7030-a641-4e4a7dde6ee2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationTechniqueAxis_01a0fcd9-76c5-7030-a641-4e4a7dde6ee2" xlink:to="loc_us-gaap_ValuationTechniqueDomain_01a0fcd9-76c5-7030-a641-4e4a7dde6ee2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain_01a0fcd9-76c5-79ab-a20d-25c4850eefb4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationTechniqueAxis_01a0fcd9-76c5-7030-a641-4e4a7dde6ee2" xlink:to="loc_us-gaap_ValuationTechniqueDomain_01a0fcd9-76c5-79ab-a20d-25c4850eefb4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDiscountedCashFlowMember_01a0fcd9-76c5-7c44-b605-70fe33cff7ac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueDiscountedCashFlowMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationTechniqueDomain_01a0fcd9-76c5-79ab-a20d-25c4850eefb4" xlink:to="loc_us-gaap_ValuationTechniqueDiscountedCashFlowMember_01a0fcd9-76c5-7c44-b605-70fe33cff7ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a13bd6-53cb-788c-a171-aa39c3c446e5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a0fcd9-76c5-7b00-a87f-0492b3473599" xlink:to="loc_us-gaap_AwardTypeAxis_01a13bd6-53cb-788c-a171-aa39c3c446e5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a13bd6-53cb-788c-a171-aa39c3c446e5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_01a13bd6-53cb-788c-a171-aa39c3c446e5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a13bd6-53cb-788c-a171-aa39c3c446e5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a13bd6-53cb-7ec5-b14a-7be6f5791fe4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_01a13bd6-53cb-788c-a171-aa39c3c446e5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a13bd6-53cb-7ec5-b14a-7be6f5791fe4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_SolarisHealthMember_01a13bdf-7c26-71bd-b330-dc1f41f752b4" xlink:href="cah-20260930.xsd#cah_SolarisHealthMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a13bd6-53cb-7ec5-b14a-7be6f5791fe4" xlink:to="loc_cah_SolarisHealthMember_01a13bdf-7c26-71bd-b330-dc1f41f752b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_01a0fcd9-76c5-7202-bc3d-5605c29ba8d9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_01a0fcd9-76c5-7202-bc3d-5605c29ba8d9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_01a0fcd9-76c5-7d38-8a2d-fefd71778fdd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_01a0fcd9-76c5-7d38-8a2d-fefd71778fdd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_01a0fcd9-76c5-745e-8444-d908ad7625d5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_01a0fcd9-76c5-745e-8444-d908ad7625d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_01a0fcd9-76c5-7a35-b92e-2fcc50ae9c8f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_01a0fcd9-76c5-7a35-b92e-2fcc50ae9c8f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_01a0fcd9-76c5-738a-aab6-6b837d137ff6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_01a0fcd9-76c5-738a-aab6-6b837d137ff6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_01a0fcd9-76c5-7a88-a469-da9c3ea1d03d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_01a0fcd9-76c5-7a88-a469-da9c3ea1d03d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_01a0fcd9-76c5-7ec9-997c-5453d5daccd9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_01a0fcd9-76c5-7ec9-997c-5453d5daccd9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_01a0fcd9-76c5-7006-b8fa-2e7df906c2a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_01a0fcd9-76c5-7006-b8fa-2e7df906c2a6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_01a0fcd9-76c5-742b-a5ee-83df491bd4e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_01a0fcd9-76c5-742b-a5ee-83df491bd4e1" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_01a0fcd9-76c5-7158-9966-a1fecac7a3e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_01a0fcd9-76c5-7158-9966-a1fecac7a3e6" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesLongTermDebt_01a0fcd9-76c5-773e-83dd-8615da5962df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesLongTermDebt_01a0fcd9-76c5-773e-83dd-8615da5962df" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_01a0fcd9-76c5-7643-bd3f-bfbff3f36b43" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_01a0fcd9-76c5-7643-bd3f-bfbff3f36b43" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_01a0fcd9-76c5-7a61-acc4-ec342759d536" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_01a0fcd9-76c5-7a61-acc4-ec342759d536" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_01a0fcd9-76c5-7a03-8125-8ea181279d2f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_01a0fcd9-76c5-7a03-8125-8ea181279d2f" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_01a0fcd9-76c5-7985-a0c3-2c3b9bd72ed8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_01a0fcd9-76c5-7985-a0c3-2c3b9bd72ed8" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue_01a0fcd9-76c5-7cb9-993d-3fafc17af5b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue_01a0fcd9-76c5-7cb9-993d-3fafc17af5b3" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_01a0fcd9-76c5-719b-bb12-f06c7c58711a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_Goodwill_01a0fcd9-76c5-719b-bb12-f06c7c58711a" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterest_01a0fcd9-76c5-7436-9eac-4a7c8fc8e8ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterest_01a0fcd9-76c5-7436-9eac-4a7c8fc8e8ad" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_01a0fcd9-76c5-785a-9f6b-6b3f82d85559" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_01a0fcd9-76c5-785a-9f6b-6b3f82d85559" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_DiscountRateFairValueInputs_01a0fcd9-76c5-7ecc-a7dd-7616a23fd7cd" xlink:href="cah-20260930.xsd#cah_DiscountRateFairValueInputs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_cah_DiscountRateFairValueInputs_01a0fcd9-76c5-7ecc-a7dd-7616a23fd7cd" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_01a0fcd9-76c5-7149-9b03-e4678b59a994" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_01a0fcd9-76c5-7149-9b03-e4678b59a994" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_IntangibleAssetsMeasurementInput_01a0fcd9-76c5-758a-b806-145e907d5e33" xlink:href="cah-20260930.xsd#cah_IntangibleAssetsMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_cah_IntangibleAssetsMeasurementInput_01a0fcd9-76c5-758a-b806-145e907d5e33" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_01a0fcd9-76c5-70a3-93b0-323c57525ad2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_01a0fcd9-76c5-70a3-93b0-323c57525ad2" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_01a13bdf-a173-78c2-9e69-78a04e418acc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a0fcd9-76c5-7eb6-adf9-34803f94ab4e" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_01a13bdf-a173-78c2-9e69-78a04e418acc" xlink:type="arc" order="23"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/RestructuringandEmployeeSeveranceLiabilitiesAssociatedwithRestructuringandEmployeeSeveranceActivitiesDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#RestructuringandEmployeeSeveranceLiabilitiesAssociatedwithRestructuringandEmployeeSeveranceActivitiesDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/RestructuringandEmployeeSeveranceLiabilitiesAssociatedwithRestructuringandEmployeeSeveranceActivitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_01a0fcd9-76c5-747c-8137-4efbc2ea8195" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_01a0fcd9-76c5-7fa4-9c55-dc4940d541a5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_01a0fcd9-76c5-747c-8137-4efbc2ea8195" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_01a0fcd9-76c5-7fa4-9c55-dc4940d541a5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_01a0fcd9-76c5-708a-9a6f-c4c41ea1a6c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_01a0fcd9-76c5-7fa4-9c55-dc4940d541a5" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_01a0fcd9-76c5-708a-9a6f-c4c41ea1a6c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_01a0fcd9-76c5-708a-9a6f-c4c41ea1a6c6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_01a0fcd9-76c5-708a-9a6f-c4c41ea1a6c6" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_01a0fcd9-76c5-708a-9a6f-c4c41ea1a6c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_01a0fcd9-76c5-7ddb-8264-e1a42fb62e30" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_01a0fcd9-76c5-708a-9a6f-c4c41ea1a6c6" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_01a0fcd9-76c5-7ddb-8264-e1a42fb62e30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_01a0fcd9-76c5-7beb-beda-fdb9fa11f79b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_01a0fcd9-76c5-7ddb-8264-e1a42fb62e30" xlink:to="loc_us-gaap_EmployeeSeveranceMember_01a0fcd9-76c5-7beb-beda-fdb9fa11f79b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FacilityClosingMember_01a0fcd9-76c5-7f04-bf03-f3e3e8d8f241" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FacilityClosingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_01a0fcd9-76c5-7ddb-8264-e1a42fb62e30" xlink:to="loc_us-gaap_FacilityClosingMember_01a0fcd9-76c5-7f04-bf03-f3e3e8d8f241" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveRollForward_01a0fcd9-76c5-7597-8477-7fd4f71de9b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringReserveRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_01a0fcd9-76c5-747c-8137-4efbc2ea8195" xlink:to="loc_us-gaap_RestructuringReserveRollForward_01a0fcd9-76c5-7597-8477-7fd4f71de9b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_01a0fcd9-76c5-752a-90cc-ad1ea241b302" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_01a0fcd9-76c5-7597-8477-7fd4f71de9b4" xlink:to="loc_us-gaap_RestructuringReserve_01a0fcd9-76c5-752a-90cc-ad1ea241b302" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCosts_01a0fcd9-76c5-7d7c-aadb-ade07e8a10dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_01a0fcd9-76c5-7597-8477-7fd4f71de9b4" xlink:to="loc_us-gaap_RestructuringCosts_01a0fcd9-76c5-7d7c-aadb-ade07e8a10dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRestructuring_01a0fcd9-76c5-72d6-ac01-5ae2988b7858" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForRestructuring"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_01a0fcd9-76c5-7597-8477-7fd4f71de9b4" xlink:to="loc_us-gaap_PaymentsForRestructuring_01a0fcd9-76c5-72d6-ac01-5ae2988b7858" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_01a0fcd9-76c5-7884-82b4-cc8662e6a49f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringReserve"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/RestructuringandEmployeeSeveranceNarrativeDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#RestructuringandEmployeeSeveranceNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/RestructuringandEmployeeSeveranceNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_01a0fcd9-76c5-73cc-b226-fc3bff791ffe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_01a0fcd9-76c5-790d-9b45-47bef2342d0e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_01a0fcd9-76c5-73cc-b226-fc3bff791ffe" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_01a0fcd9-76c5-790d-9b45-47bef2342d0e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanAxis_01a0fcd9-76c5-79bc-b3c4-8b3ca35eac42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_01a0fcd9-76c5-790d-9b45-47bef2342d0e" xlink:to="loc_us-gaap_RestructuringPlanAxis_01a0fcd9-76c5-79bc-b3c4-8b3ca35eac42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_01a0fcd9-76c5-79bc-b3c4-8b3ca35eac42_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_01a0fcd9-76c5-79bc-b3c4-8b3ca35eac42" xlink:to="loc_us-gaap_RestructuringPlanDomain_01a0fcd9-76c5-79bc-b3c4-8b3ca35eac42_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_01a0fcd9-76c5-7efc-8269-7ddbf8092fb1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_01a0fcd9-76c5-79bc-b3c4-8b3ca35eac42" xlink:to="loc_us-gaap_RestructuringPlanDomain_01a0fcd9-76c5-7efc-8269-7ddbf8092fb1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeveranceCosts1_01a0fcd9-76c5-712f-a01a-7533f434bd60" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeveranceCosts1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_01a0fcd9-76c5-73cc-b226-fc3bff791ffe" xlink:to="loc_us-gaap_SeveranceCosts1_01a0fcd9-76c5-712f-a01a-7533f434bd60" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_FacilityExitAndOtherCosts_01a0fcd9-76c5-7cba-a094-702c21543019" xlink:href="cah-20260930.xsd#cah_FacilityExitAndOtherCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_01a0fcd9-76c5-73cc-b226-fc3bff791ffe" xlink:to="loc_cah_FacilityExitAndOtherCosts_01a0fcd9-76c5-7cba-a094-702c21543019" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/GoodwillandOtherIntangibleAssetsScheduleofGoodwillbyReportableSegmentDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#GoodwillandOtherIntangibleAssetsScheduleofGoodwillbyReportableSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/GoodwillandOtherIntangibleAssetsScheduleofGoodwillbyReportableSegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_01a0fcd9-76c5-7534-a801-85b3dff5b428" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_01a0fcd9-76c5-7754-9ca7-282998da195b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_01a0fcd9-76c5-7534-a801-85b3dff5b428" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_01a0fcd9-76c5-7754-9ca7-282998da195b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-7535-93eb-f9b29ec59788" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_01a0fcd9-76c5-7754-9ca7-282998da195b" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-7535-93eb-f9b29ec59788" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7535-93eb-f9b29ec59788_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-7535-93eb-f9b29ec59788" xlink:to="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7535-93eb-f9b29ec59788_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7b0e-859a-9b73e428de83" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-7535-93eb-f9b29ec59788" xlink:to="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7b0e-859a-9b73e428de83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllOtherSegmentsMember_01a0fcd9-76c5-761d-97dd-ba55b7783dee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllOtherSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7b0e-859a-9b73e428de83" xlink:to="loc_us-gaap_AllOtherSegmentsMember_01a0fcd9-76c5-761d-97dd-ba55b7783dee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_PharmaceuticalAndSpecialtySolutionsMember_01a0fcd9-76c5-7ef3-86cb-8c34ed7f2351" xlink:href="cah-20260930.xsd#cah_PharmaceuticalAndSpecialtySolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7b0e-859a-9b73e428de83" xlink:to="loc_cah_PharmaceuticalAndSpecialtySolutionsMember_01a0fcd9-76c5-7ef3-86cb-8c34ed7f2351" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_GMPDMember_01a0fcd9-76c5-75e7-8cc9-e93fcf27ede3" xlink:href="cah-20260930.xsd#cah_GMPDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7b0e-859a-9b73e428de83" xlink:to="loc_cah_GMPDMember_01a0fcd9-76c5-75e7-8cc9-e93fcf27ede3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_01a0fcd9-76c5-7831-ae40-5c9eaf8acfc0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GoodwillRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_01a0fcd9-76c5-7534-a801-85b3dff5b428" xlink:to="loc_us-gaap_GoodwillRollForward_01a0fcd9-76c5-7831-ae40-5c9eaf8acfc0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_01a0fcd9-76c5-7c37-a755-5f6bb91152bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_01a0fcd9-76c5-7831-ae40-5c9eaf8acfc0" xlink:to="loc_us-gaap_Goodwill_01a0fcd9-76c5-7c37-a755-5f6bb91152bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_01a0fcd9-76c5-7ee6-8ded-d019f2746ca1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GoodwillAcquiredDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_01a0fcd9-76c5-7831-ae40-5c9eaf8acfc0" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_01a0fcd9-76c5-7ee6-8ded-d019f2746ca1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_01a0fcd9-76c5-7c3d-b22c-430b4c5378ee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_01a0fcd9-76c5-7a47-b0e5-82b8a993bc77" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_01a0fcd9-76c5-7e4b-b929-ba5b32cc0eaf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_01a0fcd9-76c5-7a47-b0e5-82b8a993bc77" xlink:to="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_01a0fcd9-76c5-7e4b-b929-ba5b32cc0eaf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_01a0fcd9-76c5-7f12-b529-8a791af47a2e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_01a0fcd9-76c5-7e4b-b929-ba5b32cc0eaf" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_01a0fcd9-76c5-7f12-b529-8a791af47a2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7f12-b529-8a791af47a2e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_01a0fcd9-76c5-7f12-b529-8a791af47a2e" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7f12-b529-8a791af47a2e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-705f-9afa-ba7f3c5286f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_01a0fcd9-76c5-7f12-b529-8a791af47a2e" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-705f-9afa-ba7f3c5286f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_IPRDTrademarksandOtherMember_01a0fcd9-76c5-7c52-aa69-2fcae446a4e7" xlink:href="cah-20260930.xsd#cah_IPRDTrademarksandOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-705f-9afa-ba7f3c5286f1" xlink:to="loc_cah_IPRDTrademarksandOtherMember_01a0fcd9-76c5-7c52-aa69-2fcae446a4e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_01a0fcd9-76c5-7648-8b22-d7d50bd1760c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_01a0fcd9-76c5-7a47-b0e5-82b8a993bc77" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_01a0fcd9-76c5-7648-8b22-d7d50bd1760c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_01a0fcd9-76c5-7b89-b588-4434dbb0e89f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_01a0fcd9-76c5-749c-baf1-2dd0e557cfd1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_01a0fcd9-76c5-7b89-b588-4434dbb0e89f" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_01a0fcd9-76c5-749c-baf1-2dd0e557cfd1" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_01a0fcd9-76c5-73c4-a7d0-bcde552d1a6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_01a0fcd9-76c5-749c-baf1-2dd0e557cfd1" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_01a0fcd9-76c5-73c4-a7d0-bcde552d1a6b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-73c4-a7d0-bcde552d1a6b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_01a0fcd9-76c5-73c4-a7d0-bcde552d1a6b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-73c4-a7d0-bcde552d1a6b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7580-b197-dc9ad986884d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_01a0fcd9-76c5-73c4-a7d0-bcde552d1a6b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7580-b197-dc9ad986884d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_01a0fcd9-76c5-7523-979e-a9bd9982a74c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7580-b197-dc9ad986884d" xlink:to="loc_us-gaap_CustomerRelationshipsMember_01a0fcd9-76c5-7523-979e-a9bd9982a74c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_TrademarksAndPatentsMember_01a0fcd9-76c5-70c8-80d0-8690e17e28b8" xlink:href="cah-20260930.xsd#cah_TrademarksAndPatentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7580-b197-dc9ad986884d" xlink:to="loc_cah_TrademarksAndPatentsMember_01a0fcd9-76c5-70c8-80d0-8690e17e28b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_01a0fcd9-76c5-7dc5-bd4f-a76b2e54f06c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7580-b197-dc9ad986884d" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_01a0fcd9-76c5-7dc5-bd4f-a76b2e54f06c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_01a0fcd9-76c5-7640-8e38-f1bb6332d9c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncompeteAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_01a0fcd9-76c5-7580-b197-dc9ad986884d" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_01a0fcd9-76c5-7640-8e38-f1bb6332d9c0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_01a0fcd9-76c5-7651-b770-ca2773c0e207" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_01a0fcd9-76c5-7b89-b588-4434dbb0e89f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_01a0fcd9-76c5-7651-b770-ca2773c0e207" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_01a0fcd9-76c5-7c56-aff2-63a175a4fee9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_01a0fcd9-76c5-7b89-b588-4434dbb0e89f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_01a0fcd9-76c5-7c56-aff2-63a175a4fee9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_01a0fcd9-76c5-7eef-bd34-43bc63a9d849" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_01a0fcd9-76c5-7b89-b588-4434dbb0e89f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_01a0fcd9-76c5-7eef-bd34-43bc63a9d849" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_01a0fcd9-76c5-712b-8e91-322154f1d506" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_01a0fcd9-76c5-7b89-b588-4434dbb0e89f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_01a0fcd9-76c5-712b-8e91-322154f1d506" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#GoodwillandOtherIntangibleAssetsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_01a0fcd9-76c5-7f08-acea-f88308204e0d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_01a0fcd9-76c5-7ba4-b50b-6baca7d81cb9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_01a0fcd9-76c5-7f08-acea-f88308204e0d" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_01a0fcd9-76c5-7ba4-b50b-6baca7d81cb9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-742e-9d30-330698df8960" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_01a0fcd9-76c5-7ba4-b50b-6baca7d81cb9" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-742e-9d30-330698df8960" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-742e-9d30-330698df8960_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-742e-9d30-330698df8960" xlink:to="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-742e-9d30-330698df8960_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7f3c-a70a-4650dc38a64d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-742e-9d30-330698df8960" xlink:to="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7f3c-a70a-4650dc38a64d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_GMPDMember_01a0fcd9-76c5-7018-b7f2-a726e2b0c3bd" xlink:href="cah-20260930.xsd#cah_GMPDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7f3c-a70a-4650dc38a64d" xlink:to="loc_cah_GMPDMember_01a0fcd9-76c5-7018-b7f2-a726e2b0c3bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReportingUnitAxis_01a0fcd9-76c5-7f19-9a5f-ba53a6853e28" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReportingUnitAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_01a0fcd9-76c5-7ba4-b50b-6baca7d81cb9" xlink:to="loc_us-gaap_ReportingUnitAxis_01a0fcd9-76c5-7f19-9a5f-ba53a6853e28" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReportingUnitDomain_01a0fcd9-76c5-7f19-9a5f-ba53a6853e28_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReportingUnitDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReportingUnitAxis_01a0fcd9-76c5-7f19-9a5f-ba53a6853e28" xlink:to="loc_us-gaap_ReportingUnitDomain_01a0fcd9-76c5-7f19-9a5f-ba53a6853e28_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReportingUnitDomain_01a0fcd9-76c5-7265-be40-cc30e60d9735" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReportingUnitDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReportingUnitAxis_01a0fcd9-76c5-7f19-9a5f-ba53a6853e28" xlink:to="loc_us-gaap_ReportingUnitDomain_01a0fcd9-76c5-7265-be40-cc30e60d9735" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_01a0fcd9-76c5-72d5-87ab-a61fa46cc6a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_01a0fcd9-76c5-7f08-acea-f88308204e0d" xlink:to="loc_us-gaap_Goodwill_01a0fcd9-76c5-72d5-87ab-a61fa46cc6a6" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/LongTermObligationsandOtherShortTermBorrowingsNarrativeDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#LongTermObligationsandOtherShortTermBorrowingsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/LongTermObligationsandOtherShortTermBorrowingsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_01a0fcd9-76c5-71fd-b0c2-5d369f314c50" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_01a0fcd9-76c5-7347-9abb-cfd09b8fd3bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01a0fcd9-76c5-71fd-b0c2-5d369f314c50" xlink:to="loc_us-gaap_DebtInstrumentTable_01a0fcd9-76c5-7347-9abb-cfd09b8fd3bb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_01a0fcd9-76c5-7d05-96dc-4bef67c37bf5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_01a0fcd9-76c5-7347-9abb-cfd09b8fd3bb" xlink:to="loc_us-gaap_CreditFacilityAxis_01a0fcd9-76c5-7d05-96dc-4bef67c37bf5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_01a0fcd9-76c5-7d05-96dc-4bef67c37bf5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_01a0fcd9-76c5-7d05-96dc-4bef67c37bf5" xlink:to="loc_us-gaap_CreditFacilityDomain_01a0fcd9-76c5-7d05-96dc-4bef67c37bf5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_01a0fcd9-76c5-70e2-a07c-32723a9d665b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_01a0fcd9-76c5-7d05-96dc-4bef67c37bf5" xlink:to="loc_us-gaap_CreditFacilityDomain_01a0fcd9-76c5-70e2-a07c-32723a9d665b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_01a0fcd9-76c5-7447-b554-2248410e4317" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialPaperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_01a0fcd9-76c5-70e2-a07c-32723a9d665b" xlink:to="loc_us-gaap_CommercialPaperMember_01a0fcd9-76c5-7447-b554-2248410e4317" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_01a0fcd9-76c5-7ee2-892a-7d9a4473b308" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_01a0fcd9-76c5-70e2-a07c-32723a9d665b" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_01a0fcd9-76c5-7ee2-892a-7d9a4473b308" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_A364DayRevolvingCreditFacilityMember_01a0fcd9-76c5-77a1-aadd-bea3364d64bc" xlink:href="cah-20260930.xsd#cah_A364DayRevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_01a0fcd9-76c5-70e2-a07c-32723a9d665b" xlink:to="loc_cah_A364DayRevolvingCreditFacilityMember_01a0fcd9-76c5-77a1-aadd-bea3364d64bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShortTermCreditFacilitiesMember_01a0fcd9-76c5-7236-8092-1d123002ed26" xlink:href="cah-20260930.xsd#cah_ShortTermCreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_01a0fcd9-76c5-70e2-a07c-32723a9d665b" xlink:to="loc_cah_ShortTermCreditFacilitiesMember_01a0fcd9-76c5-7236-8092-1d123002ed26" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_CommittedReceivablesSalesFacilityProgramMember_01a0fcd9-76c5-7b3b-92a7-c6011cb21b19" xlink:href="cah-20260930.xsd#cah_CommittedReceivablesSalesFacilityProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cah_ShortTermCreditFacilitiesMember_01a0fcd9-76c5-7236-8092-1d123002ed26" xlink:to="loc_cah_CommittedReceivablesSalesFacilityProgramMember_01a0fcd9-76c5-7b3b-92a7-c6011cb21b19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_UncommittedRevolvingCreditFacilityMember_01a19dcc-6a4b-7a24-bf5d-339e296522eb" xlink:href="cah-20260930.xsd#cah_UncommittedRevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_01a0fcd9-76c5-70e2-a07c-32723a9d665b" xlink:to="loc_cah_UncommittedRevolvingCreditFacilityMember_01a19dcc-6a4b-7a24-bf5d-339e296522eb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_01a0fcd9-76c5-7201-b2c3-24174ec36be5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_01a0fcd9-76c5-7347-9abb-cfd09b8fd3bb" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_01a0fcd9-76c5-7201-b2c3-24174ec36be5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_01a0fcd9-76c5-7201-b2c3-24174ec36be5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_01a0fcd9-76c5-7201-b2c3-24174ec36be5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_01a0fcd9-76c5-7201-b2c3-24174ec36be5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_01a0fcd9-76c5-7379-ae00-bfdfdac48610" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_01a0fcd9-76c5-7201-b2c3-24174ec36be5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_01a0fcd9-76c5-7379-ae00-bfdfdac48610" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_01a0fcd9-76c5-7a59-b17a-6a902f098171" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_01a0fcd9-76c5-7347-9abb-cfd09b8fd3bb" xlink:to="loc_us-gaap_VariableRateAxis_01a0fcd9-76c5-7a59-b17a-6a902f098171" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_01a0fcd9-76c5-7a59-b17a-6a902f098171_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_01a0fcd9-76c5-7a59-b17a-6a902f098171" xlink:to="loc_us-gaap_VariableRateDomain_01a0fcd9-76c5-7a59-b17a-6a902f098171_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_01a0fcd9-76c5-7d5d-a2e5-cb4fff210d90" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_01a0fcd9-76c5-7a59-b17a-6a902f098171" xlink:to="loc_us-gaap_VariableRateDomain_01a0fcd9-76c5-7d5d-a2e5-cb4fff210d90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_01a0fcd9-76c5-7312-8caa-40e322cc5b0c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_01a0fcd9-76c5-7347-9abb-cfd09b8fd3bb" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_01a0fcd9-76c5-7312-8caa-40e322cc5b0c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_01a0fcd9-76c5-7312-8caa-40e322cc5b0c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_01a0fcd9-76c5-7312-8caa-40e322cc5b0c" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_01a0fcd9-76c5-7312-8caa-40e322cc5b0c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_01a0fcd9-76c5-7ef6-97c8-404cdad5dcf2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_01a0fcd9-76c5-7312-8caa-40e322cc5b0c" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_01a0fcd9-76c5-7ef6-97c8-404cdad5dcf2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a0fcd9-76c5-76b7-bcd2-c697346a1ca4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_01a0fcd9-76c5-7347-9abb-cfd09b8fd3bb" xlink:to="loc_srt_RangeAxis_01a0fcd9-76c5-76b7-bcd2-c697346a1ca4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a0fcd9-76c5-76b7-bcd2-c697346a1ca4_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_01a0fcd9-76c5-76b7-bcd2-c697346a1ca4" xlink:to="loc_srt_RangeMember_01a0fcd9-76c5-76b7-bcd2-c697346a1ca4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a0fcd9-76c5-77e5-beae-28032128b79c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_01a0fcd9-76c5-76b7-bcd2-c697346a1ca4" xlink:to="loc_srt_RangeMember_01a0fcd9-76c5-77e5-beae-28032128b79c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_01a0fcd9-76c5-7886-b939-3f41a0954f16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_01a0fcd9-76c5-7347-9abb-cfd09b8fd3bb" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_01a0fcd9-76c5-7886-b939-3f41a0954f16" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_01a0fcd9-76c5-7886-b939-3f41a0954f16_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_01a0fcd9-76c5-7886-b939-3f41a0954f16" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_01a0fcd9-76c5-7886-b939-3f41a0954f16_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_01a0fcd9-76c5-7bf0-baa6-9ba50a1bd86a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_01a0fcd9-76c5-7886-b939-3f41a0954f16" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_01a0fcd9-76c5-7bf0-baa6-9ba50a1bd86a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_BackstopCreditFacilityMember_01a0fcd9-76c5-7ce7-b988-6d0d4bff3a84" xlink:href="cah-20260930.xsd#cah_BackstopCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_01a0fcd9-76c5-7bf0-baa6-9ba50a1bd86a" xlink:to="loc_cah_BackstopCreditFacilityMember_01a0fcd9-76c5-7ce7-b988-6d0d4bff3a84" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_MaturityDateAxis_01a164a8-4ccd-7a46-95a9-d83c2011b3c9" xlink:href="cah-20260930.xsd#cah_MaturityDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_01a0fcd9-76c5-7347-9abb-cfd09b8fd3bb" xlink:to="loc_cah_MaturityDateAxis_01a164a8-4ccd-7a46-95a9-d83c2011b3c9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_MaturityDateDomain_01a164a8-4ccd-7a46-95a9-d83c2011b3c9_default" xlink:href="cah-20260930.xsd#cah_MaturityDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_cah_MaturityDateAxis_01a164a8-4ccd-7a46-95a9-d83c2011b3c9" xlink:to="loc_cah_MaturityDateDomain_01a164a8-4ccd-7a46-95a9-d83c2011b3c9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_MaturityDateDomain_01a164a8-4ccd-7816-b3a2-415776d31e49" xlink:href="cah-20260930.xsd#cah_MaturityDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_cah_MaturityDateAxis_01a164a8-4ccd-7a46-95a9-d83c2011b3c9" xlink:to="loc_cah_MaturityDateDomain_01a164a8-4ccd-7816-b3a2-415776d31e49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_01a18953-10fc-76a0-9b97-ee8606ee3e4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_01a0fcd9-76c5-7347-9abb-cfd09b8fd3bb" xlink:to="loc_us-gaap_DebtInstrumentAxis_01a18953-10fc-76a0-9b97-ee8606ee3e4d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_01a18953-10fc-76a0-9b97-ee8606ee3e4d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_01a18953-10fc-76a0-9b97-ee8606ee3e4d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_01a18953-10fc-76a0-9b97-ee8606ee3e4d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_01a18953-10fc-7e1f-848a-a7597b7b043e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_01a18953-10fc-76a0-9b97-ee8606ee3e4d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_01a18953-10fc-7e1f-848a-a7597b7b043e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_CommittedReceivablesSalesFacilityProgramMember_01a1896b-819f-7dd8-9e61-7da909308af1" xlink:href="cah-20260930.xsd#cah_CommittedReceivablesSalesFacilityProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_01a18953-10fc-7e1f-848a-a7597b7b043e" xlink:to="loc_cah_CommittedReceivablesSalesFacilityProgramMember_01a1896b-819f-7dd8-9e61-7da909308af1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_01a19dbe-953d-7ec4-94c5-ad00521d228a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_01a0fcd9-76c5-7347-9abb-cfd09b8fd3bb" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_01a19dbe-953d-7ec4-94c5-ad00521d228a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_01a19dbe-953d-7ec4-94c5-ad00521d228a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_01a19dbe-953d-7ec4-94c5-ad00521d228a" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_01a19dbe-953d-7ec4-94c5-ad00521d228a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_01a19dbe-953d-7b93-847a-5526e726936a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_01a19dbe-953d-7ec4-94c5-ad00521d228a" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_01a19dbe-953d-7b93-847a-5526e726936a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_01a19dbe-e4a8-780e-b920-ca1c014a85e5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_01a19dbe-953d-7b93-847a-5526e726936a" xlink:to="loc_us-gaap_SubsequentEventMember_01a19dbe-e4a8-780e-b920-ca1c014a85e5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_TotalLongTermAndShortTermObligations_01a0fcd9-76c5-7c19-b83e-4d215b2e9224" xlink:href="cah-20260930.xsd#cah_TotalLongTermAndShortTermObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01a0fcd9-76c5-71fd-b0c2-5d369f314c50" xlink:to="loc_cah_TotalLongTermAndShortTermObligations_01a0fcd9-76c5-7c19-b83e-4d215b2e9224" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrentAndNoncurrent_01a0fcd9-76c5-7312-bb59-dbe13a654cce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01a0fcd9-76c5-71fd-b0c2-5d369f314c50" xlink:to="loc_us-gaap_AccountsPayableCurrentAndNoncurrent_01a0fcd9-76c5-7312-bb59-dbe13a654cce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_01a0fcd9-76c5-70ed-a523-4f92db56b283" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01a0fcd9-76c5-71fd-b0c2-5d369f314c50" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_01a0fcd9-76c5-70ed-a523-4f92db56b283" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_01a0fcd9-76c5-72fe-ad58-9e0cf802a6c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherShortTermBorrowings_01a0fcd9-76c5-7590-a334-08edf5700cf7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01a0fcd9-76c5-71fd-b0c2-5d369f314c50" xlink:to="loc_us-gaap_OtherShortTermBorrowings_01a0fcd9-76c5-7590-a334-08edf5700cf7" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/CommitmentsContingentLiabilitiesandLitigationNarrativeDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#CommitmentsContingentLiabilitiesandLitigationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/CommitmentsContingentLiabilitiesandLitigationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_01a0fcd9-76c5-7d42-9b7f-459b8af6ebba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_us-gaap_LossContingenciesTable_01a0fcd9-76c5-7d42-9b7f-459b8af6ebba" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_01a0fcd9-76c5-7ddd-a68d-e96044de72da" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0fcd9-76c5-7d42-9b7f-459b8af6ebba" xlink:to="loc_srt_MajorCustomersAxis_01a0fcd9-76c5-7ddd-a68d-e96044de72da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_01a0fcd9-76c5-7ddd-a68d-e96044de72da_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_01a0fcd9-76c5-7ddd-a68d-e96044de72da" xlink:to="loc_srt_NameOfMajorCustomerDomain_01a0fcd9-76c5-7ddd-a68d-e96044de72da_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_01a0fcd9-76c5-7896-9f82-35eec202c581" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_01a0fcd9-76c5-7ddd-a68d-e96044de72da" xlink:to="loc_srt_NameOfMajorCustomerDomain_01a0fcd9-76c5-7896-9f82-35eec202c581" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_CVSHealthMember_01a0fcd9-76c5-7635-97b7-78701e28b14d" xlink:href="cah-20260930.xsd#cah_CVSHealthMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_01a0fcd9-76c5-7896-9f82-35eec202c581" xlink:to="loc_cah_CVSHealthMember_01a0fcd9-76c5-7635-97b7-78701e28b14d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_01a0fcd9-76c5-7504-ae61-ac457da04e44" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0fcd9-76c5-7d42-9b7f-459b8af6ebba" xlink:to="loc_srt_LitigationCaseAxis_01a0fcd9-76c5-7504-ae61-ac457da04e44" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_01a0fcd9-76c5-7504-ae61-ac457da04e44_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_01a0fcd9-76c5-7504-ae61-ac457da04e44" xlink:to="loc_srt_LitigationCaseTypeDomain_01a0fcd9-76c5-7504-ae61-ac457da04e44_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_01a0fcd9-76c5-7015-8ea2-399dd481a520" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_01a0fcd9-76c5-7504-ae61-ac457da04e44" xlink:to="loc_srt_LitigationCaseTypeDomain_01a0fcd9-76c5-7015-8ea2-399dd481a520" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_OpioidLawsuitsMember_01a0fcd9-76c5-725f-8d45-f2cd3c96e415" xlink:href="cah-20260930.xsd#cah_OpioidLawsuitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_01a0fcd9-76c5-7015-8ea2-399dd481a520" xlink:to="loc_cah_OpioidLawsuitsMember_01a0fcd9-76c5-725f-8d45-f2cd3c96e415" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ClassActionLawsuitsMember_01a0fcd9-76c5-727c-884e-57719408c05f" xlink:href="cah-20260930.xsd#cah_ClassActionLawsuitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_01a0fcd9-76c5-7015-8ea2-399dd481a520" xlink:to="loc_cah_ClassActionLawsuitsMember_01a0fcd9-76c5-727c-884e-57719408c05f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_OpioidLitigationAxis_01a0fcd9-76c5-7e19-88d1-9c4bff4e06ae" xlink:href="cah-20260930.xsd#cah_OpioidLitigationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0fcd9-76c5-7d42-9b7f-459b8af6ebba" xlink:to="loc_cah_OpioidLitigationAxis_01a0fcd9-76c5-7e19-88d1-9c4bff4e06ae" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_OpioidLitigationDomain_01a0fcd9-76c5-7e19-88d1-9c4bff4e06ae_default" xlink:href="cah-20260930.xsd#cah_OpioidLitigationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_cah_OpioidLitigationAxis_01a0fcd9-76c5-7e19-88d1-9c4bff4e06ae" xlink:to="loc_cah_OpioidLitigationDomain_01a0fcd9-76c5-7e19-88d1-9c4bff4e06ae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_OpioidLitigationDomain_01a0fcd9-76c5-72a6-ae64-7002b7975fa9" xlink:href="cah-20260930.xsd#cah_OpioidLitigationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_cah_OpioidLitigationAxis_01a0fcd9-76c5-7e19-88d1-9c4bff4e06ae" xlink:to="loc_cah_OpioidLitigationDomain_01a0fcd9-76c5-72a6-ae64-7002b7975fa9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_TotalOpioidLitigationMember_01a0fcd9-76c5-7db6-83f2-b690db5e5a5d" xlink:href="cah-20260930.xsd#cah_TotalOpioidLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cah_OpioidLitigationDomain_01a0fcd9-76c5-72a6-ae64-7002b7975fa9" xlink:to="loc_cah_TotalOpioidLitigationMember_01a0fcd9-76c5-7db6-83f2-b690db5e5a5d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_LawsuitTypeAxis_01a0fcd9-76c5-73b3-9f75-859c2f96cda5" xlink:href="cah-20260930.xsd#cah_LawsuitTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0fcd9-76c5-7d42-9b7f-459b8af6ebba" xlink:to="loc_cah_LawsuitTypeAxis_01a0fcd9-76c5-73b3-9f75-859c2f96cda5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_LitigationTypeDomain_01a0fcd9-76c5-73b3-9f75-859c2f96cda5_default" xlink:href="cah-20260930.xsd#cah_LitigationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_cah_LawsuitTypeAxis_01a0fcd9-76c5-73b3-9f75-859c2f96cda5" xlink:to="loc_cah_LitigationTypeDomain_01a0fcd9-76c5-73b3-9f75-859c2f96cda5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_LitigationTypeDomain_01a0fcd9-76c5-73ad-be11-26a335623ab4" xlink:href="cah-20260930.xsd#cah_LitigationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_cah_LawsuitTypeAxis_01a0fcd9-76c5-73b3-9f75-859c2f96cda5" xlink:to="loc_cah_LitigationTypeDomain_01a0fcd9-76c5-73ad-be11-26a335623ab4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ClassActionLawsuitsMember_01a0fcd9-76c5-79e0-ab23-286778e54f5b" xlink:href="cah-20260930.xsd#cah_ClassActionLawsuitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cah_LitigationTypeDomain_01a0fcd9-76c5-73ad-be11-26a335623ab4" xlink:to="loc_cah_ClassActionLawsuitsMember_01a0fcd9-76c5-79e0-ab23-286778e54f5b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_PlaintiffTypeAxis_01a0fcd9-76c5-71da-9b4a-adfb81443a73" xlink:href="cah-20260930.xsd#cah_PlaintiffTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0fcd9-76c5-7d42-9b7f-459b8af6ebba" xlink:to="loc_cah_PlaintiffTypeAxis_01a0fcd9-76c5-71da-9b4a-adfb81443a73" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_PlaintiffTypeDomain_01a0fcd9-76c5-71da-9b4a-adfb81443a73_default" xlink:href="cah-20260930.xsd#cah_PlaintiffTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_cah_PlaintiffTypeAxis_01a0fcd9-76c5-71da-9b4a-adfb81443a73" xlink:to="loc_cah_PlaintiffTypeDomain_01a0fcd9-76c5-71da-9b4a-adfb81443a73_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_PlaintiffTypeDomain_01a0fcd9-76c5-79d4-8206-278a68b27fec" xlink:href="cah-20260930.xsd#cah_PlaintiffTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_cah_PlaintiffTypeAxis_01a0fcd9-76c5-71da-9b4a-adfb81443a73" xlink:to="loc_cah_PlaintiffTypeDomain_01a0fcd9-76c5-79d4-8206-278a68b27fec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_PrivatePartiesMember_01a0fcd9-76c5-7ca7-88f2-f406d977d80a" xlink:href="cah-20260930.xsd#cah_PrivatePartiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cah_PlaintiffTypeDomain_01a0fcd9-76c5-79d4-8206-278a68b27fec" xlink:to="loc_cah_PrivatePartiesMember_01a0fcd9-76c5-7ca7-88f2-f406d977d80a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ClassActionLawsuitsMember_01a0fcd9-76c5-7a0e-9fef-b5dee633b5ea" xlink:href="cah-20260930.xsd#cah_ClassActionLawsuitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cah_PlaintiffTypeDomain_01a0fcd9-76c5-79d4-8206-278a68b27fec" xlink:to="loc_cah_ClassActionLawsuitsMember_01a0fcd9-76c5-7a0e-9fef-b5dee633b5ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a0fcd9-76c5-75dc-bb24-bc4893896cb5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0fcd9-76c5-7d42-9b7f-459b8af6ebba" xlink:to="loc_srt_RangeAxis_01a0fcd9-76c5-75dc-bb24-bc4893896cb5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a0fcd9-76c5-75dc-bb24-bc4893896cb5_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_01a0fcd9-76c5-75dc-bb24-bc4893896cb5" xlink:to="loc_srt_RangeMember_01a0fcd9-76c5-75dc-bb24-bc4893896cb5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a0fcd9-76c5-73b7-a5ad-a8769b63a63b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_01a0fcd9-76c5-75dc-bb24-bc4893896cb5" xlink:to="loc_srt_RangeMember_01a0fcd9-76c5-73b7-a5ad-a8769b63a63b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_01a0fcd9-76c5-72f1-8158-a9328c101816" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a0fcd9-76c5-73b7-a5ad-a8769b63a63b" xlink:to="loc_srt_MinimumMember_01a0fcd9-76c5-72f1-8158-a9328c101816" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_01a0fcd9-76c5-7fc7-8594-0a5c98adf768" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a0fcd9-76c5-73b7-a5ad-a8769b63a63b" xlink:to="loc_srt_MaximumMember_01a0fcd9-76c5-7fc7-8594-0a5c98adf768" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_01a0fcd9-76c5-70e4-95b6-6f73c474a84b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0fcd9-76c5-7d42-9b7f-459b8af6ebba" xlink:to="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_01a0fcd9-76c5-70e4-95b6-6f73c474a84b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_01a0fcd9-76c5-70e4-95b6-6f73c474a84b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_01a0fcd9-76c5-70e4-95b6-6f73c474a84b" xlink:to="loc_us-gaap_LossContingencyNatureDomain_01a0fcd9-76c5-70e4-95b6-6f73c474a84b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_01a0fcd9-76c5-77e6-b3d7-c0648fc58970" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_01a0fcd9-76c5-70e4-95b6-6f73c474a84b" xlink:to="loc_us-gaap_LossContingencyNatureDomain_01a0fcd9-76c5-77e6-b3d7-c0648fc58970" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_OpioidLawsuitsMember_01a0fcd9-76c5-79d7-b80b-58151447c9c9" xlink:href="cah-20260930.xsd#cah_OpioidLawsuitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_01a0fcd9-76c5-77e6-b3d7-c0648fc58970" xlink:to="loc_cah_OpioidLawsuitsMember_01a0fcd9-76c5-79d7-b80b-58151447c9c9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_01a0fcd9-76c5-7fde-b52c-8488aa480d8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0fcd9-76c5-7d42-9b7f-459b8af6ebba" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_01a0fcd9-76c5-7fde-b52c-8488aa480d8e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_01a0fcd9-76c5-7fde-b52c-8488aa480d8e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_01a0fcd9-76c5-7fde-b52c-8488aa480d8e" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_01a0fcd9-76c5-7fde-b52c-8488aa480d8e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_01a0fcd9-76c5-77a2-b030-b7f39f388820" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_01a0fcd9-76c5-7fde-b52c-8488aa480d8e" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_01a0fcd9-76c5-77a2-b030-b7f39f388820" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_01a0fcd9-76c5-7d3c-afb6-eb281de53503" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_01a0fcd9-76c5-77a2-b030-b7f39f388820" xlink:to="loc_us-gaap_SubsequentEventMember_01a0fcd9-76c5-7d3c-afb6-eb281de53503" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_AgreementsAxis_01a0fcd9-76c5-77ac-9682-c73e883dd456" xlink:href="cah-20260930.xsd#cah_AgreementsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0fcd9-76c5-7d42-9b7f-459b8af6ebba" xlink:to="loc_cah_AgreementsAxis_01a0fcd9-76c5-77ac-9682-c73e883dd456" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_AgreementsDomain_01a0fcd9-76c5-77ac-9682-c73e883dd456_default" xlink:href="cah-20260930.xsd#cah_AgreementsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_cah_AgreementsAxis_01a0fcd9-76c5-77ac-9682-c73e883dd456" xlink:to="loc_cah_AgreementsDomain_01a0fcd9-76c5-77ac-9682-c73e883dd456_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_AgreementsDomain_01a0fcd9-76c5-7155-89d7-e30bb667043e" xlink:href="cah-20260930.xsd#cah_AgreementsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_cah_AgreementsAxis_01a0fcd9-76c5-77ac-9682-c73e883dd456" xlink:to="loc_cah_AgreementsDomain_01a0fcd9-76c5-7155-89d7-e30bb667043e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_NetOperatingLossCarrybackAxis_01a1893b-3be0-77e3-8f7f-071e62d4f442" xlink:href="cah-20260930.xsd#cah_NetOperatingLossCarrybackAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0fcd9-76c5-7d42-9b7f-459b8af6ebba" xlink:to="loc_cah_NetOperatingLossCarrybackAxis_01a1893b-3be0-77e3-8f7f-071e62d4f442" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_NetOperatingLossCarrybackDomain_01a1893b-3be0-77e3-8f7f-071e62d4f442_default" xlink:href="cah-20260930.xsd#cah_NetOperatingLossCarrybackDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_cah_NetOperatingLossCarrybackAxis_01a1893b-3be0-77e3-8f7f-071e62d4f442" xlink:to="loc_cah_NetOperatingLossCarrybackDomain_01a1893b-3be0-77e3-8f7f-071e62d4f442_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_NetOperatingLossCarrybackDomain_01a1893b-3be0-7eb3-8309-cf8f9af9b101" xlink:href="cah-20260930.xsd#cah_NetOperatingLossCarrybackDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_cah_NetOperatingLossCarrybackAxis_01a1893b-3be0-77e3-8f7f-071e62d4f442" xlink:to="loc_cah_NetOperatingLossCarrybackDomain_01a1893b-3be0-7eb3-8309-cf8f9af9b101" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_NetOperatingLossCarrybackMember_01a1893b-3be0-71d0-88f1-7ae0030a3423" xlink:href="cah-20260930.xsd#cah_NetOperatingLossCarrybackMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cah_NetOperatingLossCarrybackDomain_01a1893b-3be0-7eb3-8309-cf8f9af9b101" xlink:to="loc_cah_NetOperatingLossCarrybackMember_01a1893b-3be0-71d0-88f1-7ae0030a3423" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermPurchaseCommitmentPeriod_01a0fcd9-76c5-7066-924b-e10456665d30" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermPurchaseCommitmentPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_us-gaap_LongtermPurchaseCommitmentPeriod_01a0fcd9-76c5-7066-924b-e10456665d30" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserve_01a0fcd9-76c5-74cf-ab02-4de7db8eac7a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_us-gaap_LitigationReserve_01a0fcd9-76c5-74cf-ab02-4de7db8eac7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserveCurrent_01a0fcd9-76c5-7c21-b0c3-da834b1df58d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationReserveCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_us-gaap_LitigationReserveCurrent_01a0fcd9-76c5-7c21-b0c3-da834b1df58d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_SettlingStates_01a0fcd9-76c5-79fb-88dc-6c1e2a361e39" xlink:href="cah-20260930.xsd#cah_SettlingStates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_cah_SettlingStates_01a0fcd9-76c5-79fb-88dc-6c1e2a361e39" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_SettlingUSTerritories_01a0fcd9-76c5-736e-82fc-abb99a243c7e" xlink:href="cah-20260930.xsd#cah_SettlingUSTerritories"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_cah_SettlingUSTerritories_01a0fcd9-76c5-736e-82fc-abb99a243c7e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_PercentageSettlingSubdivisions_01a0fcd9-76c5-76ae-bae4-302c49ab8057" xlink:href="cah-20260930.xsd#cah_PercentageSettlingSubdivisions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_cah_PercentageSettlingSubdivisions_01a0fcd9-76c5-76ae-bae4-302c49ab8057" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_01a0fcd9-76c5-71f7-84e8-8560fbad8527" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingencyEstimateOfPossibleLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_01a0fcd9-76c5-71f7-84e8-8560fbad8527" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForLegalSettlements_01a0fcd9-76c5-77dd-8cd4-86ec6a3a950d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForLegalSettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_us-gaap_PaymentsForLegalSettlements_01a0fcd9-76c5-77dd-8cd4-86ec6a3a950d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossRelatedToLitigationSettlement_01a0fcd9-76c5-722d-bba5-3a77fecd7c49" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossRelatedToLitigationSettlement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_us-gaap_GainLossRelatedToLitigationSettlement_01a0fcd9-76c5-722d-bba5-3a77fecd7c49" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_IncomefromSettlementsofClassActionLawsuits_01a0fcd9-76c5-7e2a-a5fc-975a8b7486b9" xlink:href="cah-20260930.xsd#cah_IncomefromSettlementsofClassActionLawsuits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_cah_IncomefromSettlementsofClassActionLawsuits_01a0fcd9-76c5-7e2a-a5fc-975a8b7486b9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExaminationEstimateOfPossibleLoss_01a18939-742f-7e75-ac33-1a84f623a09e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExaminationEstimateOfPossibleLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_us-gaap_IncomeTaxExaminationEstimateOfPossibleLoss_01a18939-742f-7e75-ac33-1a84f623a09e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAndOtherLiabilitiesNoncurrent_01a1893b-3be0-7c49-9fc3-5dbc338b5018" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredTaxAndOtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_us-gaap_DeferredTaxAndOtherLiabilitiesNoncurrent_01a1893b-3be0-7c49-9fc3-5dbc338b5018" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_LossContingencyLawsuitsNumber_01a18951-26ae-71f3-944a-75ce39fdf806" xlink:href="cah-20260930.xsd#cah_LossContingencyLawsuitsNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0fcd9-76c5-78b5-86c2-09a29f375716" xlink:to="loc_cah_LossContingencyLawsuitsNumber_01a18951-26ae-71f3-944a-75ce39fdf806" xlink:type="arc" order="12"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/IncomeTaxesNarrativeDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#IncomeTaxesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/IncomeTaxesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardLineItems_01a0fcd9-76c5-740c-af7a-b2892b526fa8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TaxCreditCarryforwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardTable_01a0fcd9-76c5-709e-ba6e-95cff0a2e72d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TaxCreditCarryforwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_01a0fcd9-76c5-740c-af7a-b2892b526fa8" xlink:to="loc_us-gaap_TaxCreditCarryforwardTable_01a0fcd9-76c5-709e-ba6e-95cff0a2e72d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a18355-02d7-723d-a59a-b3ea9f75f2a7" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TaxCreditCarryforwardTable_01a0fcd9-76c5-709e-ba6e-95cff0a2e72d" xlink:to="loc_srt_RangeAxis_01a18355-02d7-723d-a59a-b3ea9f75f2a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a18355-02d7-723d-a59a-b3ea9f75f2a7_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_01a18355-02d7-723d-a59a-b3ea9f75f2a7" xlink:to="loc_srt_RangeMember_01a18355-02d7-723d-a59a-b3ea9f75f2a7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a18355-02d7-7c44-ace4-40e5a0e32aac" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_01a18355-02d7-723d-a59a-b3ea9f75f2a7" xlink:to="loc_srt_RangeMember_01a18355-02d7-7c44-ace4-40e5a0e32aac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_01a18355-0d36-7afa-aa69-44c8d6e875a4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a18355-02d7-7c44-ace4-40e5a0e32aac" xlink:to="loc_srt_MinimumMember_01a18355-0d36-7afa-aa69-44c8d6e875a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_01a18355-13c8-7c32-b582-45b9fe2ad61a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TaxCreditCarryforwardTable_01a0fcd9-76c5-709e-ba6e-95cff0a2e72d" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_01a18355-13c8-7c32-b582-45b9fe2ad61a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_01a18355-13c8-7c32-b582-45b9fe2ad61a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_01a18355-13c8-7c32-b582-45b9fe2ad61a" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_01a18355-13c8-7c32-b582-45b9fe2ad61a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_01a18355-13c8-7916-9562-f7b2d68b3666" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_01a18355-13c8-7c32-b582-45b9fe2ad61a" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_01a18355-13c8-7916-9562-f7b2d68b3666" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalRevenueServiceIRSMember_01a18357-5f2a-75b3-bbf4-5464c16ea588" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalRevenueServiceIRSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_01a18355-13c8-7916-9562-f7b2d68b3666" xlink:to="loc_us-gaap_InternalRevenueServiceIRSMember_01a18357-5f2a-75b3-bbf4-5464c16ea588" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_01a0fcd9-76c5-70c0-a26c-710d18abb952" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_01a0fcd9-76c5-740c-af7a-b2892b526fa8" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_01a0fcd9-76c5-70c0-a26c-710d18abb952" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefits_01a0fcd9-76c5-797a-a590-7bec4f8dc955" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecognizedTaxBenefits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_01a0fcd9-76c5-740c-af7a-b2892b526fa8" xlink:to="loc_us-gaap_UnrecognizedTaxBenefits_01a0fcd9-76c5-797a-a590-7bec4f8dc955" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_01a0fcd9-76c5-7262-bde8-f3231cb696ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_01a0fcd9-76c5-740c-af7a-b2892b526fa8" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_01a0fcd9-76c5-7262-bde8-f3231cb696ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued_01a0fcd9-76c5-7159-aaf5-03bdd8001101" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_01a0fcd9-76c5-740c-af7a-b2892b526fa8" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued_01a0fcd9-76c5-7159-aaf5-03bdd8001101" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OpenTaxYear_01a0fcd9-76c5-70c3-81b1-a911abb14086" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OpenTaxYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_01a0fcd9-76c5-740c-af7a-b2892b526fa8" xlink:to="loc_us-gaap_OpenTaxYear_01a0fcd9-76c5-70c3-81b1-a911abb14086" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/FairValueMeasurementsNarrativeDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#FairValueMeasurementsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/FairValueMeasurementsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a0fcd9-76c5-75ff-a7ba-791d3b0afbf3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a0fcd9-76c5-75ff-a7ba-791d3b0afbf3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_01a0fcd9-76c5-7204-ac62-bba3c350f551" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a0fcd9-76c5-75ff-a7ba-791d3b0afbf3" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_01a0fcd9-76c5-7204-ac62-bba3c350f551" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_01a0fcd9-76c5-7204-ac62-bba3c350f551_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_01a0fcd9-76c5-7204-ac62-bba3c350f551" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_01a0fcd9-76c5-7204-ac62-bba3c350f551_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_01a0fcd9-76c5-7c61-9be6-6be4144e4a27" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_01a0fcd9-76c5-7204-ac62-bba3c350f551" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_01a0fcd9-76c5-7c61-9be6-6be4144e4a27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_01a0fcd9-76c5-7c9e-95d1-854fa558555e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_01a0fcd9-76c5-7c61-9be6-6be4144e4a27" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_01a0fcd9-76c5-7c9e-95d1-854fa558555e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a0fcd9-76c5-7b1d-9024-40acfb2dfd84" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a0fcd9-76c5-75ff-a7ba-791d3b0afbf3" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a0fcd9-76c5-7b1d-9024-40acfb2dfd84" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-7b1d-9024-40acfb2dfd84_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a0fcd9-76c5-7b1d-9024-40acfb2dfd84" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-7b1d-9024-40acfb2dfd84_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-7aec-9ac5-76516d2a160b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a0fcd9-76c5-7b1d-9024-40acfb2dfd84" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-7aec-9ac5-76516d2a160b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_01a0fcd9-76c5-7042-8826-7a57ea8f58af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-7aec-9ac5-76516d2a160b" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_01a0fcd9-76c5-7042-8826-7a57ea8f58af" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_01a0fcd9-76c5-77b4-9363-c9b61e996934" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-7aec-9ac5-76516d2a160b" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_01a0fcd9-76c5-77b4-9363-c9b61e996934" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_01a0fcd9-76c5-73be-8cc0-2ad4c0e8c38b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-7aec-9ac5-76516d2a160b" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_01a0fcd9-76c5-73be-8cc0-2ad4c0e8c38b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel12And3Member_01a0fcd9-76c5-7275-8c10-25f70202f93d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel12And3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-7aec-9ac5-76516d2a160b" xlink:to="loc_us-gaap_FairValueInputsLevel12And3Member_01a0fcd9-76c5-7275-8c10-25f70202f93d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a17eb5-c1ad-74b9-b80d-f02ebb67e75d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a0fcd9-76c5-75ff-a7ba-791d3b0afbf3" xlink:to="loc_us-gaap_AwardTypeAxis_01a17eb5-c1ad-74b9-b80d-f02ebb67e75d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a17eb5-c1ad-74b9-b80d-f02ebb67e75d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_01a17eb5-c1ad-74b9-b80d-f02ebb67e75d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a17eb5-c1ad-74b9-b80d-f02ebb67e75d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a17eb5-c1ad-75fc-9975-e8d5cea08c12" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_01a17eb5-c1ad-74b9-b80d-f02ebb67e75d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a17eb5-c1ad-75fc-9975-e8d5cea08c12" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_TheSpecialtyAllianceUnitsMember_01a17ed4-5d0f-7482-9041-7f410225bcad" xlink:href="cah-20260930.xsd#cah_TheSpecialtyAllianceUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a17eb5-c1ad-75fc-9975-e8d5cea08c12" xlink:to="loc_cah_TheSpecialtyAllianceUnitsMember_01a17ed4-5d0f-7482-9041-7f410225bcad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_01a0fcd9-76c5-79b8-a5a5-1e493059ebb4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_01a0fcd9-76c5-79b8-a5a5-1e493059ebb4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_01a0fcd9-76c5-746a-a727-5efdcddd730b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_01a0fcd9-76c5-746a-a727-5efdcddd730b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_01a0fcd9-76c5-797a-8d9e-bea25b13e95e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_01a0fcd9-76c5-797a-8d9e-bea25b13e95e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_01a0fcd9-76c5-7cda-a012-f89dc299aa80" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_01a0fcd9-76c5-7cda-a012-f89dc299aa80" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_01a0fcd9-76c5-7362-bfb9-9b4b1a8bcc5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_01a0fcd9-76c5-7362-bfb9-9b4b1a8bcc5f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_01a0fcd9-76c5-7bc9-b5a8-6edf7d9479c7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_01a0fcd9-76c5-7c5b-a0f3-efe279289431" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_01a0fcd9-76c5-7c5b-a0f3-efe279289431" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases_01a17eae-ce67-7219-b92c-7151b3b4bded" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases_01a17eae-ce67-7219-b92c-7151b3b4bded" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityVesting_01a17eb0-56bb-7656-8fae-3f88be6f785f" xlink:href="cah-20260930.xsd#cah_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityVesting"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_cah_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityVesting_01a17eb0-56bb-7656-8fae-3f88be6f785f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityChangeInEstimatedFairValue_01a17eb1-946a-71f0-bba7-a4a3e326778e" xlink:href="cah-20260930.xsd#cah_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityChangeInEstimatedFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_cah_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityChangeInEstimatedFairValue_01a17eb1-946a-71f0-bba7-a4a3e326778e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements_01a17eb3-ae24-715a-8ff0-9ab1244957a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements_01a17eb3-ae24-715a-8ff0-9ab1244957a6" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_DiscountRateFairValueInputs_01a17ea8-cfd3-7927-9846-041fb007777e" xlink:href="cah-20260930.xsd#cah_DiscountRateFairValueInputs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_cah_DiscountRateFairValueInputs_01a17ea8-cfd3-7927-9846-041fb007777e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_01a17eb5-c1ad-7f0b-b32e-72e838909d2e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_01a17eb5-c1ad-7f0b-b32e-72e838909d2e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareBasedPaymentArrangementAcquisitionRelatedExpense_01a17eb6-ad53-7d94-aa87-4857e46b9c7f" xlink:href="cah-20260930.xsd#cah_ShareBasedPaymentArrangementAcquisitionRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_cah_ShareBasedPaymentArrangementAcquisitionRelatedExpense_01a17eb6-ad53-7d94-aa87-4857e46b9c7f" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareBasedPaymentArrangementNonAcquisitionRelatedExpense_01a17eb8-38f4-7941-888b-cc4c46068d94" xlink:href="cah-20260930.xsd#cah_ShareBasedPaymentArrangementNonAcquisitionRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7aed-87b5-2c4fbc3982bd" xlink:to="loc_cah_ShareBasedPaymentArrangementNonAcquisitionRelatedExpense_01a17eb8-38f4-7941-888b-cc4c46068d94" xlink:type="arc" order="14"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/FinancialInstrumentsNarrativeDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#FinancialInstrumentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/FinancialInstrumentsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_01a0fcd9-76c5-7eef-8b6f-3d04e24b1931" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_01a0fcd9-76c5-708f-87d7-2e4271ac6600" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_01a0fcd9-76c5-7eef-8b6f-3d04e24b1931" xlink:to="loc_us-gaap_DerivativeTable_01a0fcd9-76c5-708f-87d7-2e4271ac6600" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_01a0fcd9-76c5-7b38-a9a7-893d7802573a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_01a0fcd9-76c5-708f-87d7-2e4271ac6600" xlink:to="loc_us-gaap_HedgingDesignationAxis_01a0fcd9-76c5-7b38-a9a7-893d7802573a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_01a0fcd9-76c5-7b38-a9a7-893d7802573a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_01a0fcd9-76c5-7b38-a9a7-893d7802573a" xlink:to="loc_us-gaap_HedgingDesignationDomain_01a0fcd9-76c5-7b38-a9a7-893d7802573a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_01a0fcd9-76c5-7ac2-9642-41dc4cbacb32" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_01a0fcd9-76c5-7b38-a9a7-893d7802573a" xlink:to="loc_us-gaap_HedgingDesignationDomain_01a0fcd9-76c5-7ac2-9642-41dc4cbacb32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_01a0fcd9-76c5-77f0-b0e8-9fa1300a35f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_01a0fcd9-76c5-7ac2-9642-41dc4cbacb32" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_01a0fcd9-76c5-77f0-b0e8-9fa1300a35f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_01a0fcd9-76c5-71f9-be9c-ce8d295e58ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_01a0fcd9-76c5-708f-87d7-2e4271ac6600" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_01a0fcd9-76c5-71f9-be9c-ce8d295e58ea" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_01a0fcd9-76c5-71f9-be9c-ce8d295e58ea_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_01a0fcd9-76c5-71f9-be9c-ce8d295e58ea" xlink:to="loc_us-gaap_HedgingRelationshipDomain_01a0fcd9-76c5-71f9-be9c-ce8d295e58ea_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_01a0fcd9-76c5-7e4f-8b50-c6b8941f914d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_01a0fcd9-76c5-71f9-be9c-ce8d295e58ea" xlink:to="loc_us-gaap_HedgingRelationshipDomain_01a0fcd9-76c5-7e4f-8b50-c6b8941f914d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueHedgingMember_01a0fcd9-76c5-7e69-84d0-cbc59cdc2875" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_01a0fcd9-76c5-7e4f-8b50-c6b8941f914d" xlink:to="loc_us-gaap_FairValueHedgingMember_01a0fcd9-76c5-7e69-84d0-cbc59cdc2875" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentHedgingMember_01a0fcd9-76c5-7f22-8ef6-ac8c933bf675" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetInvestmentHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_01a0fcd9-76c5-7e4f-8b50-c6b8941f914d" xlink:to="loc_us-gaap_NetInvestmentHedgingMember_01a0fcd9-76c5-7f22-8ef6-ac8c933bf675" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_01a0fcd9-76c5-7e93-b4bb-29a05a95e44c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_01a0fcd9-76c5-708f-87d7-2e4271ac6600" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_01a0fcd9-76c5-7e93-b4bb-29a05a95e44c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_01a0fcd9-76c5-7e93-b4bb-29a05a95e44c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_01a0fcd9-76c5-7e93-b4bb-29a05a95e44c" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_01a0fcd9-76c5-7e93-b4bb-29a05a95e44c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_01a0fcd9-76c5-7257-b369-3a4cc8936c4c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_01a0fcd9-76c5-7e93-b4bb-29a05a95e44c" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_01a0fcd9-76c5-7257-b369-3a4cc8936c4c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_01a0fcd9-76c5-7486-8063-e327cf029e6f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_01a0fcd9-76c5-7257-b369-3a4cc8936c4c" xlink:to="loc_us-gaap_InterestRateSwapMember_01a0fcd9-76c5-7486-8063-e327cf029e6f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrencySwapMember_01a0fcd9-76c5-7195-a6a4-611d12190a2d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CurrencySwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_01a0fcd9-76c5-7257-b369-3a4cc8936c4c" xlink:to="loc_us-gaap_CurrencySwapMember_01a0fcd9-76c5-7195-a6a4-611d12190a2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_MaturityDateAxis_01a0fcd9-76c5-702a-9df7-ada2f09f7163" xlink:href="cah-20260930.xsd#cah_MaturityDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_01a0fcd9-76c5-708f-87d7-2e4271ac6600" xlink:to="loc_cah_MaturityDateAxis_01a0fcd9-76c5-702a-9df7-ada2f09f7163" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_MaturityDateDomain_01a0fcd9-76c5-702a-9df7-ada2f09f7163_default" xlink:href="cah-20260930.xsd#cah_MaturityDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_cah_MaturityDateAxis_01a0fcd9-76c5-702a-9df7-ada2f09f7163" xlink:to="loc_cah_MaturityDateDomain_01a0fcd9-76c5-702a-9df7-ada2f09f7163_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_MaturityDateDomain_01a0fcd9-76c5-7ea0-b4c0-7dcbbf2804cf" xlink:href="cah-20260930.xsd#cah_MaturityDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_cah_MaturityDateAxis_01a0fcd9-76c5-702a-9df7-ada2f09f7163" xlink:to="loc_cah_MaturityDateDomain_01a0fcd9-76c5-7ea0-b4c0-7dcbbf2804cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_September2027Member_01a0fcd9-76c5-763b-b8bd-ea315e09f1cb" xlink:href="cah-20260930.xsd#cah_September2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cah_MaturityDateDomain_01a0fcd9-76c5-7ea0-b4c0-7dcbbf2804cf" xlink:to="loc_cah_September2027Member_01a0fcd9-76c5-763b-b8bd-ea315e09f1cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_DateInitiatedAxis_01a0fcd9-76c5-74b6-913e-46c5c930d0bf" xlink:href="cah-20260930.xsd#cah_DateInitiatedAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_01a0fcd9-76c5-708f-87d7-2e4271ac6600" xlink:to="loc_cah_DateInitiatedAxis_01a0fcd9-76c5-74b6-913e-46c5c930d0bf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_DateInitiatedDomain_01a0fcd9-76c5-74b6-913e-46c5c930d0bf_default" xlink:href="cah-20260930.xsd#cah_DateInitiatedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_cah_DateInitiatedAxis_01a0fcd9-76c5-74b6-913e-46c5c930d0bf" xlink:to="loc_cah_DateInitiatedDomain_01a0fcd9-76c5-74b6-913e-46c5c930d0bf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_DateInitiatedDomain_01a0fcd9-76c5-7786-b4ea-c3dd8a7b1b69" xlink:href="cah-20260930.xsd#cah_DateInitiatedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_cah_DateInitiatedAxis_01a0fcd9-76c5-74b6-913e-46c5c930d0bf" xlink:to="loc_cah_DateInitiatedDomain_01a0fcd9-76c5-7786-b4ea-c3dd8a7b1b69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_September2023Member_01a0fcd9-76c5-76d4-9cb5-93cef44a591b" xlink:href="cah-20260930.xsd#cah_September2023Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cah_DateInitiatedDomain_01a0fcd9-76c5-7786-b4ea-c3dd8a7b1b69" xlink:to="loc_cah_September2023Member_01a0fcd9-76c5-76d4-9cb5-93cef44a591b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_September2025Member_01a19d0f-8a0c-7bb2-b350-7a09d30e3247" xlink:href="cah-20260930.xsd#cah_September2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cah_DateInitiatedDomain_01a0fcd9-76c5-7786-b4ea-c3dd8a7b1b69" xlink:to="loc_cah_September2025Member_01a19d0f-8a0c-7bb2-b350-7a09d30e3247" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1_01a0fcd9-76c5-74a4-b893-09020d42d11f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_01a0fcd9-76c5-7eef-8b6f-3d04e24b1931" xlink:to="loc_us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1_01a0fcd9-76c5-74a4-b893-09020d42d11f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityNotionalAmount_01a0fcd9-76c5-715f-b015-5ae4b75e9e5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLiabilityNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_01a0fcd9-76c5-7eef-8b6f-3d04e24b1931" xlink:to="loc_us-gaap_DerivativeLiabilityNotionalAmount_01a0fcd9-76c5-715f-b015-5ae4b75e9e5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_DerivativesHedgeDiscontinuancesTerminationOfHedgingInstrumentNotionalAmount_01a0fcd9-76c5-7d15-ae2a-e4db1fa0c478" xlink:href="cah-20260930.xsd#cah_DerivativesHedgeDiscontinuancesTerminationOfHedgingInstrumentNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_01a0fcd9-76c5-7eef-8b6f-3d04e24b1931" xlink:to="loc_cah_DerivativesHedgeDiscontinuancesTerminationOfHedgingInstrumentNotionalAmount_01a0fcd9-76c5-7d15-ae2a-e4db1fa0c478" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_01a0fcd9-76c5-75f2-834a-d280e9734417" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_01a0fcd9-76c5-7eef-8b6f-3d04e24b1931" xlink:to="loc_us-gaap_DerivativeNotionalAmount_01a0fcd9-76c5-75f2-834a-d280e9734417" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromHedgeInvestingActivities_01a17efa-4cad-7c54-aa8b-db685030b07a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromHedgeInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_01a0fcd9-76c5-7eef-8b6f-3d04e24b1931" xlink:to="loc_us-gaap_ProceedsFromHedgeInvestingActivities_01a17efa-4cad-7c54-aa8b-db685030b07a" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/FinancialInstrumentsSummaryofEstimatedFairValueofLongtermObligationsandOtherShorttermBorrowingsDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#FinancialInstrumentsSummaryofEstimatedFairValueofLongtermObligationsandOtherShorttermBorrowingsDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/FinancialInstrumentsSummaryofEstimatedFairValueofLongtermObligationsandOtherShorttermBorrowingsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7538-bd75-d8f555df6298" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a0fcd9-76c5-7c77-a27f-f5b14652fb23" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7538-bd75-d8f555df6298" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a0fcd9-76c5-7c77-a27f-f5b14652fb23" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a0fcd9-76c5-756a-ae32-8f07444587c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a0fcd9-76c5-7c77-a27f-f5b14652fb23" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a0fcd9-76c5-756a-ae32-8f07444587c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-756a-ae32-8f07444587c5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a0fcd9-76c5-756a-ae32-8f07444587c5" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-756a-ae32-8f07444587c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-7c75-8d7d-f028f875028d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a0fcd9-76c5-756a-ae32-8f07444587c5" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-7c75-8d7d-f028f875028d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_01a0fcd9-76c5-7574-97d6-b73c6e17d202" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0fcd9-76c5-7c75-8d7d-f028f875028d" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_01a0fcd9-76c5-7574-97d6-b73c6e17d202" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValue_01a0fcd9-76c5-7ca7-bc00-0629d26b5e55" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7538-bd75-d8f555df6298" xlink:to="loc_us-gaap_DebtInstrumentFairValue_01a0fcd9-76c5-7ca7-bc00-0629d26b5e55" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_CarryingAmountofLongTermandotherShortTermBorrowings_01a0fcd9-76c5-7e8b-a4cc-3c59e84012d0" xlink:href="cah-20260930.xsd#cah_CarryingAmountofLongTermandotherShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0fcd9-76c5-7538-bd75-d8f555df6298" xlink:to="loc_cah_CarryingAmountofLongTermandotherShortTermBorrowings_01a0fcd9-76c5-7e8b-a4cc-3c59e84012d0" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/ShareholdersEquityNarrativeDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#ShareholdersEquityNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/ShareholdersEquityNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_01a0fcd9-76c5-7654-96f5-320207121554" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_01a0fcd9-76c5-7a74-9f91-ffa8277eb294" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a0fcd9-76c5-7654-96f5-320207121554" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_01a0fcd9-76c5-7a74-9f91-ffa8277eb294" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_01a0fcd9-76c5-77a3-8610-02ad1abefd88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_01a0fcd9-76c5-7a74-9f91-ffa8277eb294" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_01a0fcd9-76c5-77a3-8610-02ad1abefd88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-77a3-8610-02ad1abefd88_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_01a0fcd9-76c5-77a3-8610-02ad1abefd88" xlink:to="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-77a3-8610-02ad1abefd88_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-7f72-914a-bc7da80fb7d9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_01a0fcd9-76c5-77a3-8610-02ad1abefd88" xlink:to="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-7f72-914a-bc7da80fb7d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_01a0fcd9-76c5-7d39-a6d9-b32fae1ac5f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-7f72-914a-bc7da80fb7d9" xlink:to="loc_us-gaap_TreasuryStockCommonMember_01a0fcd9-76c5-7d39-a6d9-b32fae1ac5f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareRepurchaseProgramAggregatePurchasePriceAxis_01a1835e-c00f-7eab-ba20-f2ff09cf1c10" xlink:href="cah-20260930.xsd#cah_ShareRepurchaseProgramAggregatePurchasePriceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_01a0fcd9-76c5-7a74-9f91-ffa8277eb294" xlink:to="loc_cah_ShareRepurchaseProgramAggregatePurchasePriceAxis_01a1835e-c00f-7eab-ba20-f2ff09cf1c10" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareRepurchaseProgramAggregatePurchasePriceDomain_01a1835e-c00f-7eab-ba20-f2ff09cf1c10_default" xlink:href="cah-20260930.xsd#cah_ShareRepurchaseProgramAggregatePurchasePriceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_cah_ShareRepurchaseProgramAggregatePurchasePriceAxis_01a1835e-c00f-7eab-ba20-f2ff09cf1c10" xlink:to="loc_cah_ShareRepurchaseProgramAggregatePurchasePriceDomain_01a1835e-c00f-7eab-ba20-f2ff09cf1c10_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareRepurchaseProgramAggregatePurchasePriceDomain_01a1835e-c00f-77b5-8cbd-cc0dbe54d9ca" xlink:href="cah-20260930.xsd#cah_ShareRepurchaseProgramAggregatePurchasePriceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_cah_ShareRepurchaseProgramAggregatePurchasePriceAxis_01a1835e-c00f-7eab-ba20-f2ff09cf1c10" xlink:to="loc_cah_ShareRepurchaseProgramAggregatePurchasePriceDomain_01a1835e-c00f-77b5-8cbd-cc0dbe54d9ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_A500MillionShareRepurchaseProgramMember_01a1835f-c774-7817-ae2f-3e1be1205b1c" xlink:href="cah-20260930.xsd#cah_A500MillionShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cah_ShareRepurchaseProgramAggregatePurchasePriceDomain_01a1835e-c00f-77b5-8cbd-cc0dbe54d9ca" xlink:to="loc_cah_A500MillionShareRepurchaseProgramMember_01a1835f-c774-7817-ae2f-3e1be1205b1c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_A375MillionShareRepurchaseProgramMember_01a18360-eea3-748c-886a-3b7fa686386c" xlink:href="cah-20260930.xsd#cah_A375MillionShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cah_ShareRepurchaseProgramAggregatePurchasePriceDomain_01a1835e-c00f-77b5-8cbd-cc0dbe54d9ca" xlink:to="loc_cah_A375MillionShareRepurchaseProgramMember_01a18360-eea3-748c-886a-3b7fa686386c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramAxis_01a0fcd9-76c5-7da5-8088-46ab51cf3c36" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_01a0fcd9-76c5-7a74-9f91-ffa8277eb294" xlink:to="loc_srt_ShareRepurchaseProgramAxis_01a0fcd9-76c5-7da5-8088-46ab51cf3c36" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_01a0fcd9-76c5-7da5-8088-46ab51cf3c36_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ShareRepurchaseProgramAxis_01a0fcd9-76c5-7da5-8088-46ab51cf3c36" xlink:to="loc_srt_ShareRepurchaseProgramDomain_01a0fcd9-76c5-7da5-8088-46ab51cf3c36_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_01a0fcd9-76c5-755c-ad2e-9585bd8fccd3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ShareRepurchaseProgramAxis_01a0fcd9-76c5-7da5-8088-46ab51cf3c36" xlink:to="loc_srt_ShareRepurchaseProgramDomain_01a0fcd9-76c5-755c-ad2e-9585bd8fccd3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_A375MillionShareRepurchaseProgramMember_01a0fcd9-76c5-71cd-a36e-02fdfbe87d8e" xlink:href="cah-20260930.xsd#cah_A375MillionShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramDomain_01a0fcd9-76c5-755c-ad2e-9585bd8fccd3" xlink:to="loc_cah_A375MillionShareRepurchaseProgramMember_01a0fcd9-76c5-71cd-a36e-02fdfbe87d8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_A500MillionShareRepurchaseProgramMember_01a1836a-cdae-7bf3-985b-2f3be5a37d85" xlink:href="cah-20260930.xsd#cah_A500MillionShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramDomain_01a0fcd9-76c5-755c-ad2e-9585bd8fccd3" xlink:to="loc_cah_A500MillionShareRepurchaseProgramMember_01a1836a-cdae-7bf3-985b-2f3be5a37d85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_01a0fcd9-76c5-7a98-a66a-d2c2d04f6fb1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a0fcd9-76c5-7654-96f5-320207121554" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_01a0fcd9-76c5-7a98-a66a-d2c2d04f6fb1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_01a0fcd9-76c5-75fa-aeb9-ae36c96a5975" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a0fcd9-76c5-7654-96f5-320207121554" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_01a0fcd9-76c5-75fa-aeb9-ae36c96a5975" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_01a0fcd9-76c5-7445-92ae-6ec16ce0ad5c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a0fcd9-76c5-7654-96f5-320207121554" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_01a0fcd9-76c5-7445-92ae-6ec16ce0ad5c" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/ShareholdersEquityChangesintheAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#ShareholdersEquityChangesintheAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/ShareholdersEquityChangesintheAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_01a0fcd9-76c5-7264-90ae-3ffd0a250e4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_01a0fcd9-76c5-75a8-aaf9-e7b75de3436a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_01a0fcd9-76c5-7264-90ae-3ffd0a250e4e" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_01a0fcd9-76c5-75a8-aaf9-e7b75de3436a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_01a0fcd9-76c5-7f02-9c53-3308d184a6c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_01a0fcd9-76c5-75a8-aaf9-e7b75de3436a" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_01a0fcd9-76c5-7f02-9c53-3308d184a6c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-7f02-9c53-3308d184a6c0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_01a0fcd9-76c5-7f02-9c53-3308d184a6c0" xlink:to="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-7f02-9c53-3308d184a6c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-770e-add2-16ca1d9ca477" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_01a0fcd9-76c5-7f02-9c53-3308d184a6c0" xlink:to="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-770e-add2-16ca1d9ca477" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember_01a0fcd9-76c5-7a53-b274-220f04550a8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-770e-add2-16ca1d9ca477" xlink:to="loc_us-gaap_AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember_01a0fcd9-76c5-7a53-b274-220f04550a8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember_01a0fcd9-76c5-72db-b999-13c93d48d774" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-770e-add2-16ca1d9ca477" xlink:to="loc_us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember_01a0fcd9-76c5-72db-b999-13c93d48d774" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_01a0fcd9-76c5-7627-82c2-353864cd8a82" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-770e-add2-16ca1d9ca477" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_01a0fcd9-76c5-7627-82c2-353864cd8a82" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeNoncontrollingInterestMember_01a0fcd9-76c5-73b3-8640-900d392856e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a0fcd9-76c5-770e-add2-16ca1d9ca477" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeNoncontrollingInterestMember_01a0fcd9-76c5-73b3-8640-900d392856e4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_01a0fcd9-76c5-7091-bfae-2428d97fd40b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_01a0fcd9-76c5-7264-90ae-3ffd0a250e4e" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_01a0fcd9-76c5-7091-bfae-2428d97fd40b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_01a0fcd9-76c5-7cc7-9902-454dc94a36f0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_01a0fcd9-76c5-7091-bfae-2428d97fd40b" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_01a0fcd9-76c5-7cc7-9902-454dc94a36f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_01a0fcd9-76c5-7f05-90f9-1eedbf22bb2b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_01a0fcd9-76c5-7091-bfae-2428d97fd40b" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_01a0fcd9-76c5-7f05-90f9-1eedbf22bb2b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_01a0fcd9-76c5-710d-b719-f1db02562d17" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_01a0fcd9-76c5-7091-bfae-2428d97fd40b" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_01a0fcd9-76c5-710d-b719-f1db02562d17" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_01a0fcd9-76c5-7707-9979-4e3cff06bdff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_01a0fcd9-76c5-7091-bfae-2428d97fd40b" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_01a0fcd9-76c5-7707-9979-4e3cff06bdff" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTax_01a0fcd9-76c5-700f-8bd2-f9632c50a615" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_01a0fcd9-76c5-7091-bfae-2428d97fd40b" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTax_01a0fcd9-76c5-700f-8bd2-f9632c50a615" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_01a0fcd9-76c5-7fa5-9940-9272d27f03a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/SegmentInformationNarrativeDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#SegmentInformationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/SegmentInformationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7dff-a556-e4e80a3fe062" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7dbe-9532-f96905f90afc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7dff-a556-e4e80a3fe062" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7dbe-9532-f96905f90afc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-771c-b3c8-51e024f2b03f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7dbe-9532-f96905f90afc" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-771c-b3c8-51e024f2b03f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-771c-b3c8-51e024f2b03f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-771c-b3c8-51e024f2b03f" xlink:to="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-771c-b3c8-51e024f2b03f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7348-960f-76f355960151" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-771c-b3c8-51e024f2b03f" xlink:to="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7348-960f-76f355960151" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_GMPDMember_01a0fcd9-76c5-733a-a618-289911ccc245" xlink:href="cah-20260930.xsd#cah_GMPDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7348-960f-76f355960151" xlink:to="loc_cah_GMPDMember_01a0fcd9-76c5-733a-a618-289911ccc245" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllOtherSegmentsMember_01a0fcd9-76c5-7370-945d-349b7e58d064" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllOtherSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7348-960f-76f355960151" xlink:to="loc_us-gaap_AllOtherSegmentsMember_01a0fcd9-76c5-7370-945d-349b7e58d064" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7dd7-86bf-46cd5c46abb4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7dbe-9532-f96905f90afc" xlink:to="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7dd7-86bf-46cd5c46abb4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7dd7-86bf-46cd5c46abb4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7dd7-86bf-46cd5c46abb4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7dd7-86bf-46cd5c46abb4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7d85-b466-a826cc49d2ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7dd7-86bf-46cd5c46abb4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7d85-b466-a826cc49d2ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_01a0fcd9-76c5-7370-8075-fb0c37b4660a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7dff-a556-e4e80a3fe062" xlink:to="loc_us-gaap_NumberOfReportableSegments_01a0fcd9-76c5-7370-8075-fb0c37b4660a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfOperatingSegments_01a0fcd9-76c5-76cb-a2af-9b30d38de449" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NumberOfOperatingSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7dff-a556-e4e80a3fe062" xlink:to="loc_us-gaap_NumberOfOperatingSegments_01a0fcd9-76c5-76cb-a2af-9b30d38de449" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ProjectCostsOnInvestmentAndOtherSpending_01a0fcd9-76c5-7252-9e39-899ccf9b7457" xlink:href="cah-20260930.xsd#cah_ProjectCostsOnInvestmentAndOtherSpending"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7dff-a556-e4e80a3fe062" xlink:to="loc_cah_ProjectCostsOnInvestmentAndOtherSpending_01a0fcd9-76c5-7252-9e39-899ccf9b7457" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/SegmentInformationRevenuebyReportableSegmentDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#SegmentInformationRevenuebyReportableSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/SegmentInformationRevenuebyReportableSegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7b31-9a35-a84b57bf91e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7cf9-8ae2-33676cc85c7f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7b31-9a35-a84b57bf91e6" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7cf9-8ae2-33676cc85c7f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-770c-ae4d-12a80ce45abb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7cf9-8ae2-33676cc85c7f" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-770c-ae4d-12a80ce45abb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-770c-ae4d-12a80ce45abb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-770c-ae4d-12a80ce45abb" xlink:to="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-770c-ae4d-12a80ce45abb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7e12-b6e3-01268a3ed2fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-770c-ae4d-12a80ce45abb" xlink:to="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7e12-b6e3-01268a3ed2fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_PharmaceuticalAndSpecialtySolutionsMember_01a0fcd9-76c5-7227-8ffe-fc4362744b59" xlink:href="cah-20260930.xsd#cah_PharmaceuticalAndSpecialtySolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7e12-b6e3-01268a3ed2fe" xlink:to="loc_cah_PharmaceuticalAndSpecialtySolutionsMember_01a0fcd9-76c5-7227-8ffe-fc4362744b59" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_GMPDMember_01a0fcd9-76c5-71d9-91f6-5345434a5b9d" xlink:href="cah-20260930.xsd#cah_GMPDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7e12-b6e3-01268a3ed2fe" xlink:to="loc_cah_GMPDMember_01a0fcd9-76c5-71d9-91f6-5345434a5b9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllOtherSegmentsMember_01a0fcd9-76c5-746d-b089-184ec3acd8ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllOtherSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7e12-b6e3-01268a3ed2fe" xlink:to="loc_us-gaap_AllOtherSegmentsMember_01a0fcd9-76c5-746d-b089-184ec3acd8ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsegmentsAxis_01a0fcd9-76c5-773c-94c5-f916a4b4d913" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7cf9-8ae2-33676cc85c7f" xlink:to="loc_us-gaap_SubsegmentsAxis_01a0fcd9-76c5-773c-94c5-f916a4b4d913" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsegmentsDomain_01a0fcd9-76c5-773c-94c5-f916a4b4d913_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsegmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsegmentsAxis_01a0fcd9-76c5-773c-94c5-f916a4b4d913" xlink:to="loc_us-gaap_SubsegmentsDomain_01a0fcd9-76c5-773c-94c5-f916a4b4d913_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsegmentsDomain_01a0fcd9-76c5-74cd-8a0b-e4c8cb379624" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsegmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsegmentsAxis_01a0fcd9-76c5-773c-94c5-f916a4b4d913" xlink:to="loc_us-gaap_SubsegmentsDomain_01a0fcd9-76c5-74cd-8a0b-e4c8cb379624" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_NuclearAndPrecisionHealthSolutionsMember_01a0fcd9-76c5-7cbb-bf26-7ed4b57da5c2" xlink:href="cah-20260930.xsd#cah_NuclearAndPrecisionHealthSolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsegmentsDomain_01a0fcd9-76c5-74cd-8a0b-e4c8cb379624" xlink:to="loc_cah_NuclearAndPrecisionHealthSolutionsMember_01a0fcd9-76c5-7cbb-bf26-7ed4b57da5c2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_AtHomeSolutionsMember_01a0fcd9-76c5-7d48-8f9e-af5ed2e79eb5" xlink:href="cah-20260930.xsd#cah_AtHomeSolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsegmentsDomain_01a0fcd9-76c5-74cd-8a0b-e4c8cb379624" xlink:to="loc_cah_AtHomeSolutionsMember_01a0fcd9-76c5-7d48-8f9e-af5ed2e79eb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_OptiFreightMember_01a0fcd9-76c5-7d27-b3ab-5ace2f2e3b8e" xlink:href="cah-20260930.xsd#cah_OptiFreightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsegmentsDomain_01a0fcd9-76c5-74cd-8a0b-e4c8cb379624" xlink:to="loc_cah_OptiFreightMember_01a0fcd9-76c5-7d27-b3ab-5ace2f2e3b8e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-79ac-b606-dacf7fd5b9cb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7cf9-8ae2-33676cc85c7f" xlink:to="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-79ac-b606-dacf7fd5b9cb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-79ac-b606-dacf7fd5b9cb_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-79ac-b606-dacf7fd5b9cb" xlink:to="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-79ac-b606-dacf7fd5b9cb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-74a6-aa65-c75c94a56909" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-79ac-b606-dacf7fd5b9cb" xlink:to="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-74a6-aa65-c75c94a56909" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_01a0fcd9-76c5-7dd1-88b2-162d1430a191" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-74a6-aa65-c75c94a56909" xlink:to="loc_us-gaap_OperatingSegmentsMember_01a0fcd9-76c5-7dd1-88b2-162d1430a191" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_01a0fcd9-76c5-759a-91d1-3e30dc74f189" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-74a6-aa65-c75c94a56909" xlink:to="loc_us-gaap_CorporateNonSegmentMember_01a0fcd9-76c5-759a-91d1-3e30dc74f189" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_01a0fcd9-76c5-74cc-aa0d-6ee52cd72e6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7b31-9a35-a84b57bf91e6" xlink:to="loc_us-gaap_Revenues_01a0fcd9-76c5-74cc-aa0d-6ee52cd72e6d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/SegmentInformationRevenuebyGeographicalSegmentsDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#SegmentInformationRevenuebyGeographicalSegmentsDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/SegmentInformationRevenuebyGeographicalSegmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_cah_SegmentRevenuebyGeographicLineItems_01a0fcd9-76c5-7eaf-8f5e-0283b197c326" xlink:href="cah-20260930.xsd#cah_SegmentRevenuebyGeographicLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_SegmentRevenuebyGeographicTable_01a0fcd9-76c5-7ddb-b2e5-60fd1fc5b5cb" xlink:href="cah-20260930.xsd#cah_SegmentRevenuebyGeographicTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_cah_SegmentRevenuebyGeographicLineItems_01a0fcd9-76c5-7eaf-8f5e-0283b197c326" xlink:to="loc_cah_SegmentRevenuebyGeographicTable_01a0fcd9-76c5-7ddb-b2e5-60fd1fc5b5cb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-79f8-8c91-074ac08261e2" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_cah_SegmentRevenuebyGeographicTable_01a0fcd9-76c5-7ddb-b2e5-60fd1fc5b5cb" xlink:to="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-79f8-8c91-074ac08261e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-79f8-8c91-074ac08261e2_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-79f8-8c91-074ac08261e2" xlink:to="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-79f8-8c91-074ac08261e2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-7d35-b569-1ec54d5f2bfb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-79f8-8c91-074ac08261e2" xlink:to="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-7d35-b569-1ec54d5f2bfb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_01a0fcd9-76c5-7d0b-ab12-a1758feadb98" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-7d35-b569-1ec54d5f2bfb" xlink:to="loc_us-gaap_OperatingSegmentsMember_01a0fcd9-76c5-7d0b-ab12-a1758feadb98" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_01a0fcd9-76c5-7381-8148-89705a297789" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-7d35-b569-1ec54d5f2bfb" xlink:to="loc_us-gaap_CorporateNonSegmentMember_01a0fcd9-76c5-7381-8148-89705a297789" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_01a0fcd9-76c5-70cb-ad69-55a26e62f521" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_cah_SegmentRevenuebyGeographicTable_01a0fcd9-76c5-7ddb-b2e5-60fd1fc5b5cb" xlink:to="loc_srt_StatementGeographicalAxis_01a0fcd9-76c5-70cb-ad69-55a26e62f521" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_01a0fcd9-76c5-70cb-ad69-55a26e62f521_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_01a0fcd9-76c5-70cb-ad69-55a26e62f521" xlink:to="loc_srt_SegmentGeographicalDomain_01a0fcd9-76c5-70cb-ad69-55a26e62f521_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_01a0fcd9-76c5-7b6e-8268-20e74d1501b8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_01a0fcd9-76c5-70cb-ad69-55a26e62f521" xlink:to="loc_srt_SegmentGeographicalDomain_01a0fcd9-76c5-7b6e-8268-20e74d1501b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_01a0fcd9-76c5-7259-96ac-147281fd828e" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_01a0fcd9-76c5-7b6e-8268-20e74d1501b8" xlink:to="loc_country_US_01a0fcd9-76c5-7259-96ac-147281fd828e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_01a0fcd9-76c5-75d4-ba1f-23902f902d9d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_01a0fcd9-76c5-7b6e-8268-20e74d1501b8" xlink:to="loc_us-gaap_NonUsMember_01a0fcd9-76c5-75d4-ba1f-23902f902d9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_01a0fcd9-76c5-772c-b2bf-3de1274e5c5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cah_SegmentRevenuebyGeographicLineItems_01a0fcd9-76c5-7eaf-8f5e-0283b197c326" xlink:to="loc_us-gaap_Revenues_01a0fcd9-76c5-772c-b2bf-3de1274e5c5f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/SegmentInformationSegmentProfitbyReportableSegmentDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#SegmentInformationSegmentProfitbyReportableSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/SegmentInformationSegmentProfitbyReportableSegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7c18-8f23-e6daf3f324ac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-79a6-a6a8-c370ebfbd6f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7c18-8f23-e6daf3f324ac" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-79a6-a6a8-c370ebfbd6f2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-7492-bbec-2421ffd44a2b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-79a6-a6a8-c370ebfbd6f2" xlink:to="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-7492-bbec-2421ffd44a2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-7492-bbec-2421ffd44a2b_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-7492-bbec-2421ffd44a2b" xlink:to="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-7492-bbec-2421ffd44a2b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-7f5a-a872-da407d58d325" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-7492-bbec-2421ffd44a2b" xlink:to="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-7f5a-a872-da407d58d325" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_01a0fcd9-76c5-71c5-9e8b-e5fb889b84d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-7f5a-a872-da407d58d325" xlink:to="loc_us-gaap_OperatingSegmentsMember_01a0fcd9-76c5-71c5-9e8b-e5fb889b84d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_01a0fcd9-76c5-7109-b5f6-775c35fc3dcf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-7f5a-a872-da407d58d325" xlink:to="loc_us-gaap_CorporateNonSegmentMember_01a0fcd9-76c5-7109-b5f6-775c35fc3dcf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-7d9f-aea9-05915c076a37" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-79a6-a6a8-c370ebfbd6f2" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-7d9f-aea9-05915c076a37" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7d9f-aea9-05915c076a37_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-7d9f-aea9-05915c076a37" xlink:to="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7d9f-aea9-05915c076a37_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7b61-b3b4-915a7a678739" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-7d9f-aea9-05915c076a37" xlink:to="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7b61-b3b4-915a7a678739" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_PharmaceuticalAndSpecialtySolutionsMember_01a0fcd9-76c5-7714-9121-b0830bcd944e" xlink:href="cah-20260930.xsd#cah_PharmaceuticalAndSpecialtySolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7b61-b3b4-915a7a678739" xlink:to="loc_cah_PharmaceuticalAndSpecialtySolutionsMember_01a0fcd9-76c5-7714-9121-b0830bcd944e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_GMPDMember_01a0fcd9-76c5-7700-bcb3-d4cdf3e8343f" xlink:href="cah-20260930.xsd#cah_GMPDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7b61-b3b4-915a7a678739" xlink:to="loc_cah_GMPDMember_01a0fcd9-76c5-7700-bcb3-d4cdf3e8343f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllOtherSegmentsMember_01a0fcd9-76c5-7b70-bb14-5590a03fad38" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllOtherSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7b61-b3b4-915a7a678739" xlink:to="loc_us-gaap_AllOtherSegmentsMember_01a0fcd9-76c5-7b70-bb14-5590a03fad38" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_01a0fcd9-76c5-7213-841a-9c458a82530f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7c18-8f23-e6daf3f324ac" xlink:to="loc_us-gaap_OperatingIncomeLoss_01a0fcd9-76c5-7213-841a-9c458a82530f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_01a0fcd9-76c5-7478-9172-aa13c3d303fb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7c18-8f23-e6daf3f324ac" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_01a0fcd9-76c5-7478-9172-aa13c3d303fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_01a0fcd9-76c5-74b2-b023-4534a3fba467" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7c18-8f23-e6daf3f324ac" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_01a0fcd9-76c5-74b2-b023-4534a3fba467" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_01a0fcd9-76c5-715d-8048-d92b738ba3eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7c18-8f23-e6daf3f324ac" xlink:to="loc_us-gaap_CostsAndExpenses_01a0fcd9-76c5-715d-8048-d92b738ba3eb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_01a17f02-1a76-7dba-ad4c-bd3c8b205355" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7c18-8f23-e6daf3f324ac" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_01a17f02-1a76-7dba-ad4c-bd3c8b205355" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/SegmentInformationAssetsbyReportableSegmentDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#SegmentInformationAssetsbyReportableSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/SegmentInformationAssetsbyReportableSegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7e29-82a7-12daf1f400fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7d10-b15b-f10b9786a515" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7e29-82a7-12daf1f400fd" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7d10-b15b-f10b9786a515" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-7cae-a5d2-0f3b4d57a679" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7d10-b15b-f10b9786a515" xlink:to="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-7cae-a5d2-0f3b4d57a679" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-7cae-a5d2-0f3b4d57a679_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-7cae-a5d2-0f3b4d57a679" xlink:to="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-7cae-a5d2-0f3b4d57a679_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-770d-8988-435a9a206245" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_01a0fcd9-76c5-7cae-a5d2-0f3b4d57a679" xlink:to="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-770d-8988-435a9a206245" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_01a0fcd9-76c5-77f9-b3bb-b651372daefe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-770d-8988-435a9a206245" xlink:to="loc_us-gaap_OperatingSegmentsMember_01a0fcd9-76c5-77f9-b3bb-b651372daefe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_01a0fcd9-76c5-7422-9e9b-6d5ddce35cf6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_01a0fcd9-76c5-770d-8988-435a9a206245" xlink:to="loc_us-gaap_CorporateNonSegmentMember_01a0fcd9-76c5-7422-9e9b-6d5ddce35cf6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-7545-844d-5e7d7a741a74" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7d10-b15b-f10b9786a515" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-7545-844d-5e7d7a741a74" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7545-844d-5e7d7a741a74_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-7545-844d-5e7d7a741a74" xlink:to="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7545-844d-5e7d7a741a74_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7885-936a-995fbe1c0e68" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a0fcd9-76c5-7545-844d-5e7d7a741a74" xlink:to="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7885-936a-995fbe1c0e68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_PharmaceuticalAndSpecialtySolutionsMember_01a0fcd9-76c5-7225-aa05-c137b03ac52a" xlink:href="cah-20260930.xsd#cah_PharmaceuticalAndSpecialtySolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7885-936a-995fbe1c0e68" xlink:to="loc_cah_PharmaceuticalAndSpecialtySolutionsMember_01a0fcd9-76c5-7225-aa05-c137b03ac52a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_GMPDMember_01a0fcd9-76c5-7ca8-b761-9324bc4820c6" xlink:href="cah-20260930.xsd#cah_GMPDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7885-936a-995fbe1c0e68" xlink:to="loc_cah_GMPDMember_01a0fcd9-76c5-7ca8-b761-9324bc4820c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllOtherSegmentsMember_01a0fcd9-76c5-7eab-80e3-9be5e47b5a6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllOtherSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0fcd9-76c5-7885-936a-995fbe1c0e68" xlink:to="loc_us-gaap_AllOtherSegmentsMember_01a0fcd9-76c5-7eab-80e3-9be5e47b5a6d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_01a0fcd9-76c5-7f1e-a3c2-e7da2c76ef0e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a0fcd9-76c5-7d10-b15b-f10b9786a515" xlink:to="loc_srt_StatementGeographicalAxis_01a0fcd9-76c5-7f1e-a3c2-e7da2c76ef0e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_01a0fcd9-76c5-7f1e-a3c2-e7da2c76ef0e_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_01a0fcd9-76c5-7f1e-a3c2-e7da2c76ef0e" xlink:to="loc_srt_SegmentGeographicalDomain_01a0fcd9-76c5-7f1e-a3c2-e7da2c76ef0e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_01a0fcd9-76c5-76b4-9d71-4b3291cc30ee" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_01a0fcd9-76c5-7f1e-a3c2-e7da2c76ef0e" xlink:to="loc_srt_SegmentGeographicalDomain_01a0fcd9-76c5-76b4-9d71-4b3291cc30ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_01a0fcd9-76c5-75b5-a472-c239532d85bd" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_01a0fcd9-76c5-76b4-9d71-4b3291cc30ee" xlink:to="loc_country_US_01a0fcd9-76c5-75b5-a472-c239532d85bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_01a0fcd9-76c5-700d-ae55-caa2af696932" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_01a0fcd9-76c5-76b4-9d71-4b3291cc30ee" xlink:to="loc_us-gaap_NonUsMember_01a0fcd9-76c5-700d-ae55-caa2af696932" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_01a0fcd9-76c5-740b-8fa2-587d93a24fc2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7e29-82a7-12daf1f400fd" xlink:to="loc_us-gaap_Assets_01a0fcd9-76c5-740b-8fa2-587d93a24fc2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_01a0fcd9-76c5-7303-b8a2-2d2edd02826b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7e29-82a7-12daf1f400fd" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_01a0fcd9-76c5-7303-b8a2-2d2edd02826b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_01a0fcd9-76c5-753f-9ef4-c73118ca5547" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentExpenditureAdditionToLongLivedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7e29-82a7-12daf1f400fd" xlink:to="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_01a0fcd9-76c5-753f-9ef4-c73118ca5547" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_01a0fcd9-76c5-7e08-bcab-de6f4a7c53a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a0fcd9-76c5-7e29-82a7-12daf1f400fd" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_01a0fcd9-76c5-7e08-bcab-de6f4a7c53a1" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/ShareBasedCompensationNarrativeDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#ShareBasedCompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/ShareBasedCompensationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-736f-8643-0f2b60159f6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7bdb-8270-8d616d32fe12" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-736f-8643-0f2b60159f6b" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7bdb-8270-8d616d32fe12" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_01a0fcd9-76c5-70fe-96ba-c4f8289b3338" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7bdb-8270-8d616d32fe12" xlink:to="loc_us-gaap_PlanNameAxis_01a0fcd9-76c5-70fe-96ba-c4f8289b3338" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_01a0fcd9-76c5-70fe-96ba-c4f8289b3338_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_01a0fcd9-76c5-70fe-96ba-c4f8289b3338" xlink:to="loc_us-gaap_PlanNameDomain_01a0fcd9-76c5-70fe-96ba-c4f8289b3338_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_01a0fcd9-76c5-75d3-98bb-3bcdedb27fd5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_01a0fcd9-76c5-70fe-96ba-c4f8289b3338" xlink:to="loc_us-gaap_PlanNameDomain_01a0fcd9-76c5-75d3-98bb-3bcdedb27fd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_A2021LTIPMember_01a0fcd9-76c5-741b-b3b0-a6b5710f1fca" xlink:href="cah-20260930.xsd#cah_A2021LTIPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_01a0fcd9-76c5-75d3-98bb-3bcdedb27fd5" xlink:to="loc_cah_A2021LTIPMember_01a0fcd9-76c5-741b-b3b0-a6b5710f1fca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7b1f-ba4a-c1367167dbb0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7bdb-8270-8d616d32fe12" xlink:to="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7b1f-ba4a-c1367167dbb0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7b1f-ba4a-c1367167dbb0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7b1f-ba4a-c1367167dbb0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7b1f-ba4a-c1367167dbb0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7840-8bcf-4c554e9916b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7b1f-ba4a-c1367167dbb0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7840-8bcf-4c554e9916b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_01a0fcd9-76c5-7838-98b2-6d5e400c497e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7840-8bcf-4c554e9916b4" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_01a0fcd9-76c5-7838-98b2-6d5e400c497e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_01a0fcd9-76c5-7869-8d45-1b81fd9f364d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7840-8bcf-4c554e9916b4" xlink:to="loc_us-gaap_PerformanceSharesMember_01a0fcd9-76c5-7869-8d45-1b81fd9f364d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_GIACommonStockMember_01a0fcd9-76c5-77bb-a608-9af479a3f3b7" xlink:href="cah-20260930.xsd#cah_GIACommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7840-8bcf-4c554e9916b4" xlink:to="loc_cah_GIACommonStockMember_01a0fcd9-76c5-77bb-a608-9af479a3f3b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_01a0fcd9-76c5-7fb5-b1c6-d347a9a2d4d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-736f-8643-0f2b60159f6b" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_01a0fcd9-76c5-7fb5-b1c6-d347a9a2d4d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_01a0fcd9-76c5-7ff3-b641-ed9cbd4f718f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-736f-8643-0f2b60159f6b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_01a0fcd9-76c5-7ff3-b641-ed9cbd4f718f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_01a0fcd9-76c5-7602-9c41-639d30395f1e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-736f-8643-0f2b60159f6b" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_01a0fcd9-76c5-7602-9c41-639d30395f1e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_01a0fcd9-76c5-7503-9c32-9a56fff8e9b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-736f-8643-0f2b60159f6b" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_01a0fcd9-76c5-7503-9c32-9a56fff8e9b7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_VestingPeriodinyearsforShares_01a0fcd9-76c5-7a98-9a74-e0af03d6d7b7" xlink:href="cah-20260930.xsd#cah_VestingPeriodinyearsforShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-736f-8643-0f2b60159f6b" xlink:to="loc_cah_VestingPeriodinyearsforShares_01a0fcd9-76c5-7a98-9a74-e0af03d6d7b7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_01a0fcd9-76c5-7453-aed2-bdd101d4aac4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-736f-8643-0f2b60159f6b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_01a0fcd9-76c5-7453-aed2-bdd101d4aac4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested_01a0fcd9-76c5-7e9b-bd46-3bc3f54f9341" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-736f-8643-0f2b60159f6b" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested_01a0fcd9-76c5-7e9b-bd46-3bc3f54f9341" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_01a0fcd9-76c5-724a-9a0e-1c266d5e2423" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareBasedPaymentArrangementAcquisitionRelatedExpense_01a0fcd9-76c5-7906-a4e2-814f3b17fad8" xlink:href="cah-20260930.xsd#cah_ShareBasedPaymentArrangementAcquisitionRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-736f-8643-0f2b60159f6b" xlink:to="loc_cah_ShareBasedPaymentArrangementAcquisitionRelatedExpense_01a0fcd9-76c5-7906-a4e2-814f3b17fad8" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareBasedPaymentArrangementNonAcquisitionRelatedExpense_01a0fcd9-76c5-71e9-891f-b5a03e4463b0" xlink:href="cah-20260930.xsd#cah_ShareBasedPaymentArrangementNonAcquisitionRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-736f-8643-0f2b60159f6b" xlink:to="loc_cah_ShareBasedPaymentArrangementNonAcquisitionRelatedExpense_01a0fcd9-76c5-71e9-891f-b5a03e4463b0" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareBasedPaymentArrangementExpenseIncreaseInFairValueOfLiabilities_01a0fcd9-76c5-70f7-a809-fbd8df0961cd" xlink:href="cah-20260930.xsd#cah_ShareBasedPaymentArrangementExpenseIncreaseInFairValueOfLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-736f-8643-0f2b60159f6b" xlink:to="loc_cah_ShareBasedPaymentArrangementExpenseIncreaseInFairValueOfLiabilities_01a0fcd9-76c5-70f7-a809-fbd8df0961cd" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/ShareBasedCompensationScheduleofTotalShareBasedCompensationExpensebyTypeofAwardDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#ShareBasedCompensationScheduleofTotalShareBasedCompensationExpensebyTypeofAwardDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/ShareBasedCompensationScheduleofTotalShareBasedCompensationExpensebyTypeofAwardDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-74ff-a5b1-f30692f94701" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-70f0-ae53-a3ace9009991" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-74ff-a5b1-f30692f94701" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-70f0-ae53-a3ace9009991" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7b13-af29-752e3bd3d703" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-70f0-ae53-a3ace9009991" xlink:to="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7b13-af29-752e3bd3d703" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7b13-af29-752e3bd3d703_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7b13-af29-752e3bd3d703" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7b13-af29-752e3bd3d703_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7555-8fd9-09f695ff4c09" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7b13-af29-752e3bd3d703" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7555-8fd9-09f695ff4c09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_01a0fcd9-76c5-767d-a7a2-9f08ad0dd57a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7555-8fd9-09f695ff4c09" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_01a0fcd9-76c5-767d-a7a2-9f08ad0dd57a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_01a0fcd9-76c5-771a-9de3-8a8147eb707e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7555-8fd9-09f695ff4c09" xlink:to="loc_us-gaap_PerformanceSharesMember_01a0fcd9-76c5-771a-9de3-8a8147eb707e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_GIACommonStockMember_01a0fcd9-76c5-79c6-8128-cb6894d41732" xlink:href="cah-20260930.xsd#cah_GIACommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7555-8fd9-09f695ff4c09" xlink:to="loc_cah_GIACommonStockMember_01a0fcd9-76c5-79c6-8128-cb6894d41732" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_01a0fcd9-76c5-7753-93f0-956ad7ff9d3c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-74ff-a5b1-f30692f94701" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_01a0fcd9-76c5-7753-93f0-956ad7ff9d3c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/ShareBasedCompensationScheduleofAllTransactionsRelatedtoRestrictedShareUnitsUnderthePlansDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#ShareBasedCompensationScheduleofAllTransactionsRelatedtoRestrictedShareUnitsUnderthePlansDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/ShareBasedCompensationScheduleofAllTransactionsRelatedtoRestrictedShareUnitsUnderthePlansDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-72b0-9b94-20fa6b0de332" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7be2-98a9-5e8d03b0d144" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-72b0-9b94-20fa6b0de332" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7be2-98a9-5e8d03b0d144" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-745f-b2f9-221333ceaa6c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7be2-98a9-5e8d03b0d144" xlink:to="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-745f-b2f9-221333ceaa6c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-745f-b2f9-221333ceaa6c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-745f-b2f9-221333ceaa6c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-745f-b2f9-221333ceaa6c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7c9b-8161-d0e78006b5aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-745f-b2f9-221333ceaa6c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7c9b-8161-d0e78006b5aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_01a0fcd9-76c5-766b-9bd8-b90d733a5529" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7c9b-8161-d0e78006b5aa" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_01a0fcd9-76c5-766b-9bd8-b90d733a5529" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_01a0fcd9-76c5-71ea-ab5d-133a61942cc1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-72b0-9b94-20fa6b0de332" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_01a0fcd9-76c5-71ea-ab5d-133a61942cc1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested_01a0fcd9-76c5-785e-83cc-da496bc06896" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-72b0-9b94-20fa6b0de332" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested_01a0fcd9-76c5-785e-83cc-da496bc06896" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_01a0fcd9-76c5-7e0e-bce7-d4caa7c6cc73" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-72b0-9b94-20fa6b0de332" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_01a0fcd9-76c5-7e0e-bce7-d4caa7c6cc73" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0fcd9-76c5-7a10-b19a-3dbcf23799eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-72b0-9b94-20fa6b0de332" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0fcd9-76c5-7a10-b19a-3dbcf23799eb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0fcd9-76c5-7359-825f-9dc5b2d55b71" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0fcd9-76c5-7a10-b19a-3dbcf23799eb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0fcd9-76c5-7359-825f-9dc5b2d55b71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0fcd9-76c5-7905-b7db-c0567acbf9a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0fcd9-76c5-7a10-b19a-3dbcf23799eb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0fcd9-76c5-7905-b7db-c0567acbf9a4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a0fcd9-76c5-78f5-be91-b2c8f164fc01" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0fcd9-76c5-7a10-b19a-3dbcf23799eb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a0fcd9-76c5-78f5-be91-b2c8f164fc01" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_01a0fcd9-76c5-79a2-9f18-10466ebc4ed4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0fcd9-76c5-7a10-b19a-3dbcf23799eb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_01a0fcd9-76c5-79a2-9f18-10466ebc4ed4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0fcd9-76c5-7383-9ec2-139472714dd6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0fcd9-76c5-73e9-8e7d-3cd55ef6902a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-72b0-9b94-20fa6b0de332" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0fcd9-76c5-73e9-8e7d-3cd55ef6902a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7c91-8b4a-fe873b816c38" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0fcd9-76c5-73e9-8e7d-3cd55ef6902a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7c91-8b4a-fe873b816c38" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7f05-a34a-db66370f488d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0fcd9-76c5-73e9-8e7d-3cd55ef6902a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7f05-a34a-db66370f488d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7d62-960c-62906f42ab90" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0fcd9-76c5-73e9-8e7d-3cd55ef6902a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7d62-960c-62906f42ab90" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_01a0fcd9-76c5-75e5-9b84-fa5e5e048446" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0fcd9-76c5-73e9-8e7d-3cd55ef6902a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_01a0fcd9-76c5-75e5-9b84-fa5e5e048446" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7c28-a11d-c44862d78dc7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/ShareBasedCompensationScheduleofAllTransactionsRelatedtoPerformanceShareUnitsUnderthePlansDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#ShareBasedCompensationScheduleofAllTransactionsRelatedtoPerformanceShareUnitsUnderthePlansDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/ShareBasedCompensationScheduleofAllTransactionsRelatedtoPerformanceShareUnitsUnderthePlansDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-73fe-b97b-ced773aa6c65" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-76bb-ad8c-0f2ed82f8f48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-73fe-b97b-ced773aa6c65" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-76bb-ad8c-0f2ed82f8f48" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-712c-8847-f1e16841d2d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-76bb-ad8c-0f2ed82f8f48" xlink:to="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-712c-8847-f1e16841d2d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-712c-8847-f1e16841d2d0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-712c-8847-f1e16841d2d0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-712c-8847-f1e16841d2d0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7b81-9fb9-2f8d70608753" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-712c-8847-f1e16841d2d0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7b81-9fb9-2f8d70608753" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_01a0fcd9-76c5-7da8-a855-a190917f347d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7b81-9fb9-2f8d70608753" xlink:to="loc_us-gaap_PerformanceSharesMember_01a0fcd9-76c5-7da8-a855-a190917f347d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a18dc6-5eae-7132-aeca-79622b70f0de" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-76bb-ad8c-0f2ed82f8f48" xlink:to="loc_srt_RangeAxis_01a18dc6-5eae-7132-aeca-79622b70f0de" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a18dc6-5eae-7132-aeca-79622b70f0de_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_01a18dc6-5eae-7132-aeca-79622b70f0de" xlink:to="loc_srt_RangeMember_01a18dc6-5eae-7132-aeca-79622b70f0de_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a18dc6-5eae-7a5d-b342-a82142c56f5e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_01a18dc6-5eae-7132-aeca-79622b70f0de" xlink:to="loc_srt_RangeMember_01a18dc6-5eae-7a5d-b342-a82142c56f5e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_01a18dc6-8a26-7e61-bbd5-ff8ff9a2f115" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a18dc6-5eae-7a5d-b342-a82142c56f5e" xlink:to="loc_srt_MinimumMember_01a18dc6-8a26-7e61-bbd5-ff8ff9a2f115" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_01a18dca-3ae5-76df-bbac-64552290ad80" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a18dc6-5eae-7a5d-b342-a82142c56f5e" xlink:to="loc_srt_MaximumMember_01a18dca-3ae5-76df-bbac-64552290ad80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_01a0fcd9-76c5-79e2-a34c-9c2283693810" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-73fe-b97b-ced773aa6c65" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_01a0fcd9-76c5-79e2-a34c-9c2283693810" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_01a0fcd9-76c5-7590-9b46-f3ff6f53ae19" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-73fe-b97b-ced773aa6c65" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_01a0fcd9-76c5-7590-9b46-f3ff6f53ae19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_01a0fcd9-76c5-7046-ba04-53d559626a99" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-73fe-b97b-ced773aa6c65" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_01a0fcd9-76c5-7046-ba04-53d559626a99" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0fcd9-76c5-7606-af8f-d01acd35d9f6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-73fe-b97b-ced773aa6c65" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0fcd9-76c5-7606-af8f-d01acd35d9f6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0fcd9-76c5-7819-946b-4a273b5c2b94" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0fcd9-76c5-7606-af8f-d01acd35d9f6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0fcd9-76c5-7819-946b-4a273b5c2b94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0fcd9-76c5-720a-a354-556dc22c1330" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0fcd9-76c5-7606-af8f-d01acd35d9f6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0fcd9-76c5-720a-a354-556dc22c1330" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a0fcd9-76c5-7f3e-8ac2-5900407863b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0fcd9-76c5-7606-af8f-d01acd35d9f6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a0fcd9-76c5-7f3e-8ac2-5900407863b3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_01a0fcd9-76c5-70fb-a70d-c272923de60c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0fcd9-76c5-7606-af8f-d01acd35d9f6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_01a0fcd9-76c5-70fb-a70d-c272923de60c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0fcd9-76c5-774b-b778-d3dbd08cc6a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0fcd9-76c5-7d53-aa16-d475490bc583" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-73fe-b97b-ced773aa6c65" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0fcd9-76c5-7d53-aa16-d475490bc583" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7b8c-a49b-d6dd2a63f1ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0fcd9-76c5-7d53-aa16-d475490bc583" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7b8c-a49b-d6dd2a63f1ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7310-afc2-30bf805c69ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0fcd9-76c5-7d53-aa16-d475490bc583" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7310-afc2-30bf805c69ab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7485-b726-3ce0d9709f7e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0fcd9-76c5-7d53-aa16-d475490bc583" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7485-b726-3ce0d9709f7e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7440-bf04-efff61d94159" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0fcd9-76c5-7d53-aa16-d475490bc583" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7440-bf04-efff61d94159" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7f04-8e47-482c7671afbd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cardinal.com/role/ShareBasedCompensationDetails" xlink:type="simple" xlink:href="cah-20260930.xsd#ShareBasedCompensationDetails"/>
  <link:definitionLink xlink:role="http://www.cardinal.com/role/ShareBasedCompensationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7b37-9e1e-d3491441b265" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7b37-9e1e-d3491441b265" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7475-8a31-06973de83254" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7b37-9e1e-d3491441b265" xlink:to="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7475-8a31-06973de83254" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7475-8a31-06973de83254_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7475-8a31-06973de83254" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-7475-8a31-06973de83254_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-70d9-bcda-9685cec158c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_01a0fcd9-76c5-7475-8a31-06973de83254" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-70d9-bcda-9685cec158c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_GIAUnitsMember_01a0fcd9-76c5-7d45-8b22-d9cdec80e2bf" xlink:href="cah-20260930.xsd#cah_GIAUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0fcd9-76c5-70d9-bcda-9685cec158c5" xlink:to="loc_cah_GIAUnitsMember_01a0fcd9-76c5-7d45-8b22-d9cdec80e2bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardDateAxis_01a0fcd9-76c5-7f62-92fb-3511f166a93a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7b37-9e1e-d3491441b265" xlink:to="loc_us-gaap_AwardDateAxis_01a0fcd9-76c5-7f62-92fb-3511f166a93a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardDateDomain_01a0fcd9-76c5-7f62-92fb-3511f166a93a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardDateAxis_01a0fcd9-76c5-7f62-92fb-3511f166a93a" xlink:to="loc_us-gaap_AwardDateDomain_01a0fcd9-76c5-7f62-92fb-3511f166a93a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardDateDomain_01a0fcd9-76c5-75dc-a860-1190a6564940" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardDateAxis_01a0fcd9-76c5-7f62-92fb-3511f166a93a" xlink:to="loc_us-gaap_AwardDateDomain_01a0fcd9-76c5-75dc-a860-1190a6564940" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusAxis_01a0fcd9-76c5-7cea-bb94-d2352a334f92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GranteeStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7b37-9e1e-d3491441b265" xlink:to="loc_us-gaap_GranteeStatusAxis_01a0fcd9-76c5-7cea-bb94-d2352a334f92" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_01a0fcd9-76c5-7cea-bb94-d2352a334f92_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GranteeStatusAxis_01a0fcd9-76c5-7cea-bb94-d2352a334f92" xlink:to="loc_us-gaap_GranteeStatusDomain_01a0fcd9-76c5-7cea-bb94-d2352a334f92_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_01a0fcd9-76c5-7c35-ac49-a868b33e78fb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GranteeStatusAxis_01a0fcd9-76c5-7cea-bb94-d2352a334f92" xlink:to="loc_us-gaap_GranteeStatusDomain_01a0fcd9-76c5-7c35-ac49-a868b33e78fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_01a0fcd9-76c5-7d9b-a351-51949dbe0701" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7b37-9e1e-d3491441b265" xlink:to="loc_us-gaap_PlanNameAxis_01a0fcd9-76c5-7d9b-a351-51949dbe0701" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_01a0fcd9-76c5-7d9b-a351-51949dbe0701_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_01a0fcd9-76c5-7d9b-a351-51949dbe0701" xlink:to="loc_us-gaap_PlanNameDomain_01a0fcd9-76c5-7d9b-a351-51949dbe0701_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_01a0fcd9-76c5-7c14-868a-d9d192d7e8e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_01a0fcd9-76c5-7d9b-a351-51949dbe0701" xlink:to="loc_us-gaap_PlanNameDomain_01a0fcd9-76c5-7c14-868a-d9d192d7e8e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_01a0fcd9-76c5-773a-a6b0-d806bac44ad2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7b37-9e1e-d3491441b265" xlink:to="loc_us-gaap_VestingAxis_01a0fcd9-76c5-773a-a6b0-d806bac44ad2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_01a0fcd9-76c5-773a-a6b0-d806bac44ad2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_01a0fcd9-76c5-773a-a6b0-d806bac44ad2" xlink:to="loc_us-gaap_VestingDomain_01a0fcd9-76c5-773a-a6b0-d806bac44ad2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_01a0fcd9-76c5-762f-ac96-2ee811ad941e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_01a0fcd9-76c5-773a-a6b0-d806bac44ad2" xlink:to="loc_us-gaap_VestingDomain_01a0fcd9-76c5-762f-ac96-2ee811ad941e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_01a0fcd9-76c5-76ef-a69c-49eaa0962002" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7b37-9e1e-d3491441b265" xlink:to="loc_us-gaap_StatementClassOfStockAxis_01a0fcd9-76c5-76ef-a69c-49eaa0962002" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_01a0fcd9-76c5-76ef-a69c-49eaa0962002_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_01a0fcd9-76c5-76ef-a69c-49eaa0962002" xlink:to="loc_us-gaap_ClassOfStockDomain_01a0fcd9-76c5-76ef-a69c-49eaa0962002_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_01a0fcd9-76c5-735d-a41b-ae9709963b93" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_01a0fcd9-76c5-76ef-a69c-49eaa0962002" xlink:to="loc_us-gaap_ClassOfStockDomain_01a0fcd9-76c5-735d-a41b-ae9709963b93" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a0fcd9-76c5-7e5f-9f45-0674cfae2894" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0fcd9-76c5-7b37-9e1e-d3491441b265" xlink:to="loc_srt_RangeAxis_01a0fcd9-76c5-7e5f-9f45-0674cfae2894" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a0fcd9-76c5-7e5f-9f45-0674cfae2894_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_01a0fcd9-76c5-7e5f-9f45-0674cfae2894" xlink:to="loc_srt_RangeMember_01a0fcd9-76c5-7e5f-9f45-0674cfae2894_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a0fcd9-76c5-7fac-9c32-9fe0a17f3fa0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_01a0fcd9-76c5-7e5f-9f45-0674cfae2894" xlink:to="loc_srt_RangeMember_01a0fcd9-76c5-7fac-9c32-9fe0a17f3fa0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareBasedPaymentArrangementNonAcquisitionRelatedExpense_01a0fcd9-76c5-7b7c-a401-bf50c4bdb8bb" xlink:href="cah-20260930.xsd#cah_ShareBasedPaymentArrangementNonAcquisitionRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_cah_ShareBasedPaymentArrangementNonAcquisitionRelatedExpense_01a0fcd9-76c5-7b7c-a401-bf50c4bdb8bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0fcd9-76c5-721e-bec3-585e3df329ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0fcd9-76c5-721e-bec3-585e3df329ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7396-9b6f-f8cf046afcb8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7396-9b6f-f8cf046afcb8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber_01a0fcd9-76c5-70a1-9d86-d820fff91ebe" xlink:href="cah-20260930.xsd#cah_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_cah_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber_01a0fcd9-76c5-70a1-9d86-d820fff91ebe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageGrantDateFairValue_01a0fcd9-76c5-733b-8ace-b098d83ded92" xlink:href="cah-20260930.xsd#cah_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_cah_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageGrantDateFairValue_01a0fcd9-76c5-733b-8ace-b098d83ded92" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0fcd9-76c5-7520-b35e-fc73cba4e5d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0fcd9-76c5-7520-b35e-fc73cba4e5d7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7565-8b58-16595906bef8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7565-8b58-16595906bef8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a0fcd9-76c5-7f97-88b9-60fe4aee5dd0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a0fcd9-76c5-7f97-88b9-60fe4aee5dd0" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7ce9-8446-a0f8183be6af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7ce9-8446-a0f8183be6af" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_01a0fcd9-76c5-76f9-ac1a-34073ef78e8b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_01a0fcd9-76c5-76f9-ac1a-34073ef78e8b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7307-aa7a-870b0e045491" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_01a0fcd9-76c5-7307-aa7a-870b0e045491" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareBasedPaymentArrangementNonAcquisitionRelatedExpense_01a0fcd9-76c5-784f-9726-2f59ea196d20" xlink:href="cah-20260930.xsd#cah_ShareBasedPaymentArrangementNonAcquisitionRelatedExpense"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_01a0fcd9-76c5-7ae5-a5ad-9db725c45a89" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_01a0fcd9-76c5-7ae5-a5ad-9db725c45a89" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_cah_ShareBasedPaymentArrangementExpenseIncreaseInFairValueOfLiabilities_01a0fcd9-76c5-74b8-a8b6-c3ed66423547" xlink:href="cah-20260930.xsd#cah_ShareBasedPaymentArrangementExpenseIncreaseInFairValueOfLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0fcd9-76c5-7b08-9121-9a9d0c5fc75e" xlink:to="loc_cah_ShareBasedPaymentArrangementExpenseIncreaseInFairValueOfLiabilities_01a0fcd9-76c5-74b8-a8b6-c3ed66423547" xlink:type="arc" order="13"/>
  </link:definitionLink>
</link:linkbase>
