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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019e1d2f-9a71-71df-bc00-ba86bcda75f0,g:3f84d90a-c98e-4c8e-9d8c-c01a420a9a38-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:tmo="http://thermofisher.com/20251231" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2024-01-31" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://thermofisher.com/20251231">
  <xs:import namespace="http://fasb.org/us-gaap-ebp/2026" schemaLocation="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd"/>
  <xs:import namespace="http://fasb.org/us-gaap/2026" schemaLocation="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/dtr/type/2024-01-31" schemaLocation="https://www.xbrl.org/dtr/type/2024-01-31/types.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei/2026" schemaLocation="https://xbrl.sec.gov/dei/2026/dei-2026.xsd"/>
  <xs:annotation>
    <xs:appinfo>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="tmo-20251231_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="tmo-20251231_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="tmo-20251231_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="tmo-20251231_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="Cover" roleURI="http://thermofisher.com/role/Cover">
        <link:definition>0000001 - Document - Cover</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanStatementofNetAssetAvailableforBenefitStatement" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanStatementofNetAssetAvailableforBenefitStatement">
        <link:definition>0000002 - Statement - Employee Benefit Plan, Statement of Net Asset Available for Benefit (Statement)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanStatementofChangeinNetAssetAvailableforBenefitStatement" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanStatementofChangeinNetAssetAvailableforBenefitStatement">
        <link:definition>0000003 - Statement - Employee Benefit Plan, Statement of Change in Net Asset Available for Benefit (Statement)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanDescriptionofPlan" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanDescriptionofPlan">
        <link:definition>0000004 - Disclosure - Employee Benefit Plan, Description of Plan</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanSummaryofAccountingPolicy" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanSummaryofAccountingPolicy">
        <link:definition>0000005 - Disclosure - Employee Benefit Plan, Summary of Accounting Policy</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanTaxStatus" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanTaxStatus">
        <link:definition>0000006 - Disclosure - Employee Benefit Plan, Tax Status</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanFairValueandNAV" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanFairValueandNAV">
        <link:definition>0000007 - Disclosure - Employee Benefit Plan, Fair Value and NAV</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanRelatedPartyandPartyinInterestTransactions" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanRelatedPartyandPartyinInterestTransactions">
        <link:definition>0000008 - Disclosure - Employee Benefit Plan, Related-Party and Party-in-Interest Transactions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanPlanTermination" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanPlanTermination">
        <link:definition>0000009 - Disclosure - Employee Benefit Plan, Plan Termination</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanReconciliationofFinancialStatementtoForm5500" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanReconciliationofFinancialStatementtoForm5500">
        <link:definition>0000010 - Disclosure - Employee Benefit Plan, Reconciliation of Financial Statement to Form 5500</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanScheduleAssetHeldforInvestment" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanScheduleAssetHeldforInvestment">
        <link:definition>0000011 - Disclosure - Employee Benefit Plan, Schedule, Asset Held for Investment</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanSummaryofAccountingPolicyPolicies" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanSummaryofAccountingPolicyPolicies">
        <link:definition>0000012 - Disclosure - Employee Benefit Plan, Summary of Accounting Policy (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanFairValueandNAVTables" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanFairValueandNAVTables">
        <link:definition>0000013 - Disclosure - Employee Benefit Plan, Fair Value and NAV (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanReconciliationofFinancialStatementtoForm5500Tables" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanReconciliationofFinancialStatementtoForm5500Tables">
        <link:definition>0000014 - Disclosure - Employee Benefit Plan, Reconciliation of Financial Statement to Form 5500 (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanDescriptionofPlanDetails" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanDescriptionofPlanDetails">
        <link:definition>0000015 - Disclosure - Employee Benefit Plan, Description of Plan (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanSummaryofAccountingPolicyDetails" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanSummaryofAccountingPolicyDetails">
        <link:definition>0000016 - Disclosure - Employee Benefit Plan, Summary of Accounting Policy (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanTaxStatusDetails" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanTaxStatusDetails">
        <link:definition>0000017 - Disclosure - Employee Benefit Plan, Tax Status (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanFairValueandNAVDetailsFairValueHierarchy" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanFairValueandNAVDetailsFairValueHierarchy">
        <link:definition>0000018 - Disclosure - Employee Benefit Plan, Fair Value and NAV (Details - Fair Value Hierarchy)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanFairValueandNAVDetailsNAVPracticalExpedient" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanFairValueandNAVDetailsNAVPracticalExpedient">
        <link:definition>0000019 - Disclosure - Employee Benefit Plan, Fair Value and NAV (Details - NAV Practical Expedient)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanRelatedPartyandPartyinInterestTransactionsDetails" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanRelatedPartyandPartyinInterestTransactionsDetails">
        <link:definition>0000020 - Disclosure - Employee Benefit Plan, Related-Party and Party-in-Interest Transactions (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanReconciliationofFinancialStatementtoForm5500Details" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanReconciliationofFinancialStatementtoForm5500Details">
        <link:definition>0000021 - Disclosure - Employee Benefit Plan, Reconciliation of Financial Statement to Form 5500 (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanScheduleAssetHeldforInvestmentDetails" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanScheduleAssetHeldforInvestmentDetails">
        <link:definition>0000022 - Disclosure - Employee Benefit Plan, Schedule, Asset Held for Investment (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanScheduleAssetHeldforInvestmentDetails_1" roleURI="http://thermofisher.com/role/EmployeeBenefitPlanScheduleAssetHeldforInvestmentDetails_1">
        <link:definition>0000022 - Disclosure - Employee Benefit Plan, Schedule, Asset Held for Investment (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xs:appinfo>
  </xs:annotation>
  <xs:element id="tmo_EBP001Member" abstract="true" name="EBP001Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="tmo_EbpEmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseAfterTransfers" abstract="false" name="EbpEmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseAfterTransfers" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="tmo_EBPEmployeeBenefitPlanParticipantContributionPretaxAndRothMaximumAnnualCompensationToTotalCompensationPercentage" abstract="false" name="EBPEmployeeBenefitPlanParticipantContributionPretaxAndRothMaximumAnnualCompensationToTotalCompensationPercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="tmo_EBPParticipantContributionAfterTaxMaximumAnnualContributionToEligibleCompensationPercentage" abstract="false" name="EBPParticipantContributionAfterTaxMaximumAnnualContributionToEligibleCompensationPercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="tmo_EBPVestingPercentage" abstract="false" name="EBPVestingPercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="tmo_EBPVestingServiceRequirementPeriodEmployerContributions" abstract="false" name="EBPVestingServiceRequirementPeriodEmployerContributions" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="tmo_EBPNoteReceivableFromParticipantLoanTerm" abstract="false" name="EBPNoteReceivableFromParticipantLoanTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="tmo_EBPNoteReceivableFromParticipantLoanTermForPrimaryResidence" abstract="false" name="EBPNoteReceivableFromParticipantLoanTermForPrimaryResidence" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="tmo_EBPNoteReceivableFromParticipantInterestRateRangeLowEnd" abstract="false" name="EBPNoteReceivableFromParticipantInterestRateRangeLowEnd" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="tmo_EBPNoteReceivableFromParticipantInterestRateRangeHighEnd" abstract="false" name="EBPNoteReceivableFromParticipantInterestRateRangeHighEnd" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="tmo_EBPAdministrativeExpensesPaidFromPlanLevelAccount" abstract="false" name="EBPAdministrativeExpensesPaidFromPlanLevelAccount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="tmo_EBPRevenueCredit" abstract="false" name="EBPRevenueCredit" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="tmo_EBPPlanLevelAccountBalance" abstract="false" name="EBPPlanLevelAccountBalance" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="tmo_EBPStableValueInvestmentMember" abstract="true" name="EBPStableValueInvestmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="tmo_EBPAssetAllocationFundsMember" abstract="true" name="EBPAssetAllocationFundsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="tmo_EBPRelatedPartyAndPartyInInterestDividendIncome" abstract="false" name="EBPRelatedPartyAndPartyInInterestDividendIncome" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
</xs:schema>
