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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019e6f8d-ae55-732a-a0ad-1089bdc9d209,g:0ab3eaf0-5a37-4100-b4ee-b6fe3d8bcda0-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:pubm="http://pubmatic.com/20260630" 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://pubmatic.com/20260630">
  <xs:import namespace="http://fasb.org/srt/2026" schemaLocation="https://xbrl.fasb.org/srt/2026/elts/srt-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/country/2026" schemaLocation="https://xbrl.sec.gov/country/2026/country-2026.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei/2026" schemaLocation="https://xbrl.sec.gov/dei/2026/dei-2026.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/ecd/2026" schemaLocation="https://xbrl.sec.gov/ecd/2026/ecd-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="pubm-20260630_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="pubm-20260630_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="pubm-20260630_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="pubm-20260630_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="COVER" roleURI="http://pubmatic.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="CONDENSEDCONSOLIDATEDBALANCESHEETS" roleURI="http://pubmatic.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS">
        <link:definition>9952151 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</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="CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" roleURI="http://pubmatic.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical">
        <link:definition>9952152 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</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="CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" roleURI="http://pubmatic.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS">
        <link:definition>9952153 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</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="CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSS" roleURI="http://pubmatic.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSS">
        <link:definition>9952154 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</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="CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" roleURI="http://pubmatic.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY">
        <link:definition>9952155 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS&#8217; EQUITY</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="CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" roleURI="http://pubmatic.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS">
        <link:definition>9952156 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</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="OrganizationandDescriptionofBusiness" roleURI="http://pubmatic.com/role/OrganizationandDescriptionofBusiness">
        <link:definition>9952157 - Disclosure - Organization and Description of Business</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="BasisofPresentationandSummaryofSignificantAccountingPolicies" roleURI="http://pubmatic.com/role/BasisofPresentationandSummaryofSignificantAccountingPolicies">
        <link:definition>9952158 - Disclosure - Basis of Presentation and Summary of Significant Accounting 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="FairValueMeasurements" roleURI="http://pubmatic.com/role/FairValueMeasurements">
        <link:definition>9952159 - Disclosure - Fair Value Measurements</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="BalanceSheetComponents" roleURI="http://pubmatic.com/role/BalanceSheetComponents">
        <link:definition>9952160 - Disclosure - Balance Sheet Components</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="SeniorSecuredCreditFacilitiesAgreement" roleURI="http://pubmatic.com/role/SeniorSecuredCreditFacilitiesAgreement">
        <link:definition>9952161 - Disclosure - Senior Secured Credit Facilities Agreement</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="Leases" roleURI="http://pubmatic.com/role/Leases">
        <link:definition>9952162 - Disclosure - Leases</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="AcquisitionrelatedIntangibleAssetsNet" roleURI="http://pubmatic.com/role/AcquisitionrelatedIntangibleAssetsNet">
        <link:definition>9952163 - Disclosure - Acquisition-related Intangible Assets, Net</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="CommitmentsandContingencies" roleURI="http://pubmatic.com/role/CommitmentsandContingencies">
        <link:definition>9952164 - Disclosure - Commitments and Contingencies</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="StockholdersEquityandEquityIncentivePlans" roleURI="http://pubmatic.com/role/StockholdersEquityandEquityIncentivePlans">
        <link:definition>9952165 - Disclosure - Stockholders&#8217; Equity and Equity Incentive Plans</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="NetLossPerShare" roleURI="http://pubmatic.com/role/NetLossPerShare">
        <link:definition>9952166 - Disclosure - Net Loss Per Share</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="IncomeTaxes" roleURI="http://pubmatic.com/role/IncomeTaxes">
        <link:definition>9952167 - Disclosure - Income Taxes</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="SegmentandGeographicalInformation" roleURI="http://pubmatic.com/role/SegmentandGeographicalInformation">
        <link:definition>9952168 - Disclosure - Segment and Geographical Information</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="A401kPlan" roleURI="http://pubmatic.com/role/A401kPlan">
        <link:definition>9952169 - Disclosure - 401(k) 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="SubsequentEvent" roleURI="http://pubmatic.com/role/SubsequentEvent">
        <link:definition>9952170 - Disclosure - Subsequent Event</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="BasisofPresentationandSummaryofSignificantAccountingPoliciesPolicies" roleURI="http://pubmatic.com/role/BasisofPresentationandSummaryofSignificantAccountingPoliciesPolicies">
        <link:definition>9955511 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies (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="BasisofPresentationandSummaryofSignificantAccountingPoliciesTables" roleURI="http://pubmatic.com/role/BasisofPresentationandSummaryofSignificantAccountingPoliciesTables">
        <link:definition>9955512 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies (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="FairValueMeasurementsTables" roleURI="http://pubmatic.com/role/FairValueMeasurementsTables">
        <link:definition>9955513 - Disclosure - Fair Value Measurements (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="BalanceSheetComponentsTables" roleURI="http://pubmatic.com/role/BalanceSheetComponentsTables">
        <link:definition>9955514 - Disclosure - Balance Sheet Components (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="LeasesTables" roleURI="http://pubmatic.com/role/LeasesTables">
        <link:definition>9955515 - Disclosure - Leases (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="AcquisitionrelatedIntangibleAssetsNetTables" roleURI="http://pubmatic.com/role/AcquisitionrelatedIntangibleAssetsNetTables">
        <link:definition>9955516 - Disclosure - Acquisition-related Intangible Assets, Net (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="StockholdersEquityandEquityIncentivePlansTables" roleURI="http://pubmatic.com/role/StockholdersEquityandEquityIncentivePlansTables">
        <link:definition>9955517 - Disclosure - Stockholders&#8217; Equity and Equity Incentive Plans (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="NetLossPerShareTables" roleURI="http://pubmatic.com/role/NetLossPerShareTables">
        <link:definition>9955518 - Disclosure - Net Loss Per Share (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="SegmentandGeographicalInformationTables" roleURI="http://pubmatic.com/role/SegmentandGeographicalInformationTables">
        <link:definition>9955519 - Disclosure - Segment and Geographical Information (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="BasisofPresentationandSummaryofSignificantAccountingPoliciesConcentrationRiskPercentageDetails" roleURI="http://pubmatic.com/role/BasisofPresentationandSummaryofSignificantAccountingPoliciesConcentrationRiskPercentageDetails">
        <link:definition>9955520 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies - Concentration Risk Percentage (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="BasisofPresentationandSummaryofSignificantAccountingPoliciesScheduleofAllowanceforCreditLossesDetails" roleURI="http://pubmatic.com/role/BasisofPresentationandSummaryofSignificantAccountingPoliciesScheduleofAllowanceforCreditLossesDetails">
        <link:definition>9955521 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Allowance for Credit Losses (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="FairValueMeasurementsDetails" roleURI="http://pubmatic.com/role/FairValueMeasurementsDetails">
        <link:definition>9955522 - Disclosure - Fair Value Measurements (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="BalanceSheetComponentsScheduleofMarketableSecuritiesDetails" roleURI="http://pubmatic.com/role/BalanceSheetComponentsScheduleofMarketableSecuritiesDetails">
        <link:definition>9955523 - Disclosure - Balance Sheet Components - Schedule of Marketable Securities (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="BalanceSheetComponentsNarrativeDetails" roleURI="http://pubmatic.com/role/BalanceSheetComponentsNarrativeDetails">
        <link:definition>9955524 - Disclosure - Balance Sheet Components - Narrative (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="BalanceSheetComponentsScheduleofPropertyEquipmentandSoftwareNetDetails" roleURI="http://pubmatic.com/role/BalanceSheetComponentsScheduleofPropertyEquipmentandSoftwareNetDetails">
        <link:definition>9955525 - Disclosure - Balance Sheet Components - Schedule of Property, Equipment and Software, Net (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="BalanceSheetComponentsScheduleofAccountsPayableDetails" roleURI="http://pubmatic.com/role/BalanceSheetComponentsScheduleofAccountsPayableDetails">
        <link:definition>9955526 - Disclosure - Balance Sheet Components - Schedule of Accounts Payable (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="BalanceSheetComponentsScheduleofAccruedLiabilitiesDetails" roleURI="http://pubmatic.com/role/BalanceSheetComponentsScheduleofAccruedLiabilitiesDetails">
        <link:definition>9955527 - Disclosure - Balance Sheet Components - Schedule of Accrued Liabilities (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="SeniorSecuredCreditFacilitiesAgreementDetails" roleURI="http://pubmatic.com/role/SeniorSecuredCreditFacilitiesAgreementDetails">
        <link:definition>9955528 - Disclosure - Senior Secured Credit Facilities Agreement (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="LeasesScheduleofOperatingandFinanceLeaseCostDetails" roleURI="http://pubmatic.com/role/LeasesScheduleofOperatingandFinanceLeaseCostDetails">
        <link:definition>9955529 - Disclosure - Leases - Schedule of Operating and Finance Lease Cost (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="LeasesNarrativeDetails" roleURI="http://pubmatic.com/role/LeasesNarrativeDetails">
        <link:definition>9955530 - Disclosure - Leases - Narrative (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="LeasesScheduleofLeaseMaturityDetails" roleURI="http://pubmatic.com/role/LeasesScheduleofLeaseMaturityDetails">
        <link:definition>9955531 - Disclosure - Leases - Schedule of Lease Maturity (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="LeasesScheduleofLeaseMaturityDetails_1" roleURI="http://pubmatic.com/role/LeasesScheduleofLeaseMaturityDetails_1">
        <link:definition>9955531 - Disclosure - Leases - Schedule of Lease Maturity (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="AcquisitionrelatedIntangibleAssetsNetScheduleofAcquisitionRelatedIntangibleAssetsNetDetails" roleURI="http://pubmatic.com/role/AcquisitionrelatedIntangibleAssetsNetScheduleofAcquisitionRelatedIntangibleAssetsNetDetails">
        <link:definition>9955532 - Disclosure - Acquisition-related Intangible Assets, Net - Schedule of Acquisition-Related Intangible Assets, Net (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="AcquisitionrelatedIntangibleAssetsNetNarrativeDetails" roleURI="http://pubmatic.com/role/AcquisitionrelatedIntangibleAssetsNetNarrativeDetails">
        <link:definition>9955533 - Disclosure - Acquisition-related Intangible Assets, Net - Narrative (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="AcquisitionrelatedIntangibleAssetsNetScheduleofEstimatedFutureAmortizationDetails" roleURI="http://pubmatic.com/role/AcquisitionrelatedIntangibleAssetsNetScheduleofEstimatedFutureAmortizationDetails">
        <link:definition>9955534 - Disclosure - Acquisition-related Intangible Assets, Net - Schedule of Estimated Future Amortization (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="CommitmentsandContingenciesDetails" roleURI="http://pubmatic.com/role/CommitmentsandContingenciesDetails">
        <link:definition>9955535 - Disclosure - Commitments and Contingencies (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="StockholdersEquityandEquityIncentivePlansNarrativeDetails" roleURI="http://pubmatic.com/role/StockholdersEquityandEquityIncentivePlansNarrativeDetails">
        <link:definition>9955536 - Disclosure - Stockholders&#8217; Equity and Equity Incentive Plans - Narrative (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="StockholdersEquityandEquityIncentivePlansScheduleofStockOptionActivityandRelatedInformationDetails" roleURI="http://pubmatic.com/role/StockholdersEquityandEquityIncentivePlansScheduleofStockOptionActivityandRelatedInformationDetails">
        <link:definition>9955537 - Disclosure - Stockholders&#8217; Equity and Equity Incentive Plans - Schedule of Stock Option Activity and Related Information (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="StockholdersEquityandEquityIncentivePlansScheduleofRestrictedStockUnitsandRelatedInformationDetails" roleURI="http://pubmatic.com/role/StockholdersEquityandEquityIncentivePlansScheduleofRestrictedStockUnitsandRelatedInformationDetails">
        <link:definition>9955538 - Disclosure - Stockholders&#8217; Equity and Equity Incentive Plans - Schedule of Restricted Stock Units and Related Information (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="StockholdersEquityandEquityIncentivePlansScheduleofStockbasedCompensationExpenseDetails" roleURI="http://pubmatic.com/role/StockholdersEquityandEquityIncentivePlansScheduleofStockbasedCompensationExpenseDetails">
        <link:definition>9955539 - Disclosure - Stockholders&#8217; Equity and Equity Incentive Plans - Schedule of Stock-based Compensation Expense (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="StockholdersEquityandEquityIncentivePlansScheduleofStockbasedCompensationExpenseDetails_1" roleURI="http://pubmatic.com/role/StockholdersEquityandEquityIncentivePlansScheduleofStockbasedCompensationExpenseDetails_1">
        <link:definition>9955539 - Disclosure - Stockholders&#8217; Equity and Equity Incentive Plans - Schedule of Stock-based Compensation Expense (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="NetLossPerShareScheduleofBasicandDilutedNetIncomeLossperShareDetails" roleURI="http://pubmatic.com/role/NetLossPerShareScheduleofBasicandDilutedNetIncomeLossperShareDetails">
        <link:definition>9955540 - Disclosure - Net Loss Per Share - Schedule of Basic and Diluted Net Income (Loss) per Share (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="NetLossPerShareScheduleofAntidilutiveSecuritiesExcludedfromComputationofEarningsperShareDetails" roleURI="http://pubmatic.com/role/NetLossPerShareScheduleofAntidilutiveSecuritiesExcludedfromComputationofEarningsperShareDetails">
        <link:definition>9955541 - Disclosure - Net Loss Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings per Share (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="IncomeTaxesDetails" roleURI="http://pubmatic.com/role/IncomeTaxesDetails">
        <link:definition>9955542 - Disclosure - Income Taxes (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="SegmentandGeographicalInformationNarrativeDetails" roleURI="http://pubmatic.com/role/SegmentandGeographicalInformationNarrativeDetails">
        <link:definition>9955543 - Disclosure - Segment and Geographical Information - Narrative (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="SegmentandGeographicalInformationScheduleofSegmentReportingInformationDetails" roleURI="http://pubmatic.com/role/SegmentandGeographicalInformationScheduleofSegmentReportingInformationDetails">
        <link:definition>9955544 - Disclosure - Segment and Geographical Information - Schedule of Segment Reporting Information (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="SegmentandGeographicalInformationScheduleofGeographicalInformationDetails" roleURI="http://pubmatic.com/role/SegmentandGeographicalInformationScheduleofGeographicalInformationDetails">
        <link:definition>9955545 - Disclosure - Segment and Geographical Information - Schedule of Geographical Information (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="A401kPlanDetails" roleURI="http://pubmatic.com/role/A401kPlanDetails">
        <link:definition>9955546 - Disclosure - 401(k) Plan (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="pubm_NonCashLeaseExpense" abstract="false" name="NonCashLeaseExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_StockBasedCompensationCapitalizedAsInternalUseSoftwareCosts" abstract="false" name="StockBasedCompensationCapitalizedAsInternalUseSoftwareCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_PropertyAndEquipmentIncludedInAccountsPayableAndAccruedExpenses" abstract="false" name="PropertyAndEquipmentIncludedInAccountsPayableAndAccruedExpenses" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_BuyerOneMember" abstract="true" name="BuyerOneMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_BuyerTwoMember" abstract="true" name="BuyerTwoMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_BuyerThreeMember" abstract="true" name="BuyerThreeMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_PropertyPlantAndEquipmentExcludingSoftwareInternallyDevelopedMember" abstract="true" name="PropertyPlantAndEquipmentExcludingSoftwareInternallyDevelopedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_CreditAgreementMember" abstract="true" name="CreditAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_SwinglineSubFacilityMember" abstract="true" name="SwinglineSubFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_AlternateBaseRateMember" abstract="true" name="AlternateBaseRateMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_ApplicableInterestRateMember" abstract="true" name="ApplicableInterestRateMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_LineOfCreditFacilityAccordionFeatureIncreaseLimit" abstract="false" name="LineOfCreditFacilityAccordionFeatureIncreaseLimit" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_LesseeOperatingLeaseLiabilityToBePaidAfterYearFor" abstract="false" name="LesseeOperatingLeaseLiabilityToBePaidAfterYearFor" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_FinanceLeaseLiabilityToBePaidAfterYearFour" abstract="false" name="FinanceLeaseLiabilityToBePaidAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_TotalOperatingAndFinanceLeasesAbstract" abstract="true" name="TotalOperatingAndFinanceLeasesAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="pubm_LesseeOperatingAndFinanceLeaseLiabilityToBePaidRemainderOfFiscalYear" abstract="false" name="LesseeOperatingAndFinanceLeaseLiabilityToBePaidRemainderOfFiscalYear" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_LesseeOperatingAndFinanceLeaseLiabilityToBePaidYearOne" abstract="false" name="LesseeOperatingAndFinanceLeaseLiabilityToBePaidYearOne" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_LesseeOperatingAndFinanceLeaseLiabilityToBePaidYearTwo" abstract="false" name="LesseeOperatingAndFinanceLeaseLiabilityToBePaidYearTwo" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_LesseeOperatingAndFinanceLeaseLiabilityToBePaidYearThree" abstract="false" name="LesseeOperatingAndFinanceLeaseLiabilityToBePaidYearThree" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_LesseeOperatingAndFinanceLeaseLiabilityToBePaidYearFour" abstract="false" name="LesseeOperatingAndFinanceLeaseLiabilityToBePaidYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_LesseeOperatingAndFinanceLeaseLiabilityToBePaidAfterYearFour" abstract="false" name="LesseeOperatingAndFinanceLeaseLiabilityToBePaidAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_LesseeOperatingAndFinanceLeaseLiabilityToBePaid" abstract="false" name="LesseeOperatingAndFinanceLeaseLiabilityToBePaid" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_LesseeOperatingAndFinanceLeaseLiabilityUndiscountedExcessAmount" abstract="false" name="LesseeOperatingAndFinanceLeaseLiabilityUndiscountedExcessAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_OperatingAndFinanceLeaseLiability" abstract="false" name="OperatingAndFinanceLeaseLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_IrrevocableLettersOfCreditDueJuly2028Member" abstract="true" name="IrrevocableLettersOfCreditDueJuly2028Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_IrrevocableLettersOfCreditDueApril2036Member" abstract="true" name="IrrevocableLettersOfCreditDueApril2036Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_IrrevocableLettersOfCreditDueSeptember2031Member" abstract="true" name="IrrevocableLettersOfCreditDueSeptember2031Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_NumberOfDebtInstruments" abstract="false" name="NumberOfDebtInstruments" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="pubm_A2023RepurchaseProgramMember" abstract="true" name="A2023RepurchaseProgramMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_A2024RepurchaseProgramMember" abstract="true" name="A2024RepurchaseProgramMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_A2025RepurchaseProgramMember" abstract="true" name="A2025RepurchaseProgramMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_ShareRepurchaseProgramAdditionalAuthorizedAmount" abstract="false" name="ShareRepurchaseProgramAdditionalAuthorizedAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_ShareBasedCompensationArrangementAutomaticAnnualIncreaseTerm" abstract="false" name="ShareBasedCompensationArrangementAutomaticAnnualIncreaseTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="pubm_ShareBasedCompensationArrangementByShareBasedPaymentAwardAmountWithheldForEmployeeStockPurchasePlan" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAmountWithheldForEmployeeStockPurchasePlan" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_ReportableSegmentMember" abstract="true" name="ReportableSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_RestOfTheWorldMember" abstract="true" name="RestOfTheWorldMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_StevenPantelickMember" abstract="true" name="StevenPantelickMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_LisaGimbelMember" abstract="true" name="LisaGimbelMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="pubm_AmarGoelMember" abstract="true" name="AmarGoelMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
