<?xml version="1.0" encoding="us-ascii"?>
<!-- DFIN ActiveDisclosure(SM) XBRL Schema Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date      : 2021-05-06T01:41:08.0042510+00:00 -->
<!-- Version            : 5.0.1.615 -->
<!-- Package ID         : b69aca12c2594b47b7352fa2f37ea3a6 -->
<!-- Copyright (c) 2021 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
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  <xsd:element id="qnst_ScheduleOfEarningsPerShareBasicAndDilutedTable" name="ScheduleOfEarningsPerShareBasicAndDilutedTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_PostClosingPaymentsRelatedToAcquisitionsMember" name="PostClosingPaymentsRelatedToAcquisitionsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_ContingentConsiderationRelatedToAcquisitionsMember" name="ContingentConsiderationRelatedToAcquisitionsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_CashAndCashEquivalentsAtFairValue" name="CashAndCashEquivalentsAtFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="qnst_FairValueLiabilitiesLevel3ToLevel1TransfersAmount" name="FairValueLiabilitiesLevel3ToLevel1TransfersAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="qnst_FairValueAssetsLevel3ToLevel1TransfersAmount" name="FairValueAssetsLevel3ToLevel1TransfersAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="qnst_PartnershipAgreementTerm" name="PartnershipAgreementTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="qnst_UpfrontCashPayment" name="UpfrontCashPayment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="qnst_AmortizationOfUpfrontCashPayment" name="AmortizationOfUpfrontCashPayment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="qnst_CurrentPortionOfUpfrontCashPayment" name="CurrentPortionOfUpfrontCashPayment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="qnst_PrepaidExpensesAndOtherAssetsLineItems" name="PrepaidExpensesAndOtherAssetsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_ScheduleOfPrepaidExpensesAndOtherAssetsTable" name="ScheduleOfPrepaidExpensesAndOtherAssetsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_PartnershipAgreementMember" name="PartnershipAgreementMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_QuinStreetBrasilOnlineMarketingMidiaLtdaQSBAndVEMMLLCVEMMMember" name="QuinStreetBrasilOnlineMarketingMidiaLtdaQSBAndVEMMLLCVEMMMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_EuroDemandDoBrasilServicosDeGeracaoDeLeadsLtdaEDBMember" name="EuroDemandDoBrasilServicosDeGeracaoDeLeadsLtdaEDBMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_PurchasePriceOfAgreement" name="PurchasePriceOfAgreement" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="qnst_CashPaidForNetAssets" name="CashPaidForNetAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="qnst_BusinessCombinationDeferredConsideration" name="BusinessCombinationDeferredConsideration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="qnst_BusinessCombinationDeferredConsiderationLiabilityPaymentPeriod" name="BusinessCombinationDeferredConsiderationLiabilityPaymentPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="qnst_BusinessCombinationDeferredConsiderationArrangementsDescription" name="BusinessCombinationDeferredConsiderationArrangementsDescription" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="qnst_MayoLabsLLCMember" name="MayoLabsLLCMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_AmOneCorporationMember" name="AmOneCorporationMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_CloudControlMediaLLCMember" name="CloudControlMediaLLCMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_MyBankTrackerComLLCMember" name="MyBankTrackerComLLCMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_DeferredConsiderationImputedInterest" name="DeferredConsiderationImputedInterest" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="qnst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseRightOfUseAsset" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseRightOfUseAsset" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="qnst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseLiability" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="qnst_PreliminaryMember" name="PreliminaryMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_YearToDateAdjustmentsMember" name="YearToDateAdjustmentsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_IncrementalTaxExpenses" name="IncrementalTaxExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="qnst_ContentMember" name="ContentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_WebsiteTradeDomainNamesMember" name="WebsiteTradeDomainNamesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_AcquiredTechnologyAndOthersMember" name="AcquiredTechnologyAndOthersMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_BusinessCombinationAdditionalContingentConsiderationPayable" name="BusinessCombinationAdditionalContingentConsiderationPayable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="qnst_BusinessCombinationContingentConsiderationPayablePeriod" name="BusinessCombinationContingentConsiderationPayablePeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="qnst_AcquiredIndefiniteLivedIntangibleAssetsWeightedAverageUsefulLife" name="AcquiredIndefiniteLivedIntangibleAssetsWeightedAverageUsefulLife" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="qnst_IncreaseInOperatingLeaseLiabilityInExchangeForRightOfUseAssetObtained" name="IncreaseInOperatingLeaseLiabilityInExchangeForRightOfUseAssetObtained" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="qnst_CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract" name="CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_LeaseLiablitiesArisingFromObtainingRightOfUseAssetsAbstract" name="LeaseLiablitiesArisingFromObtainingRightOfUseAssetsAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_FuturePrincipalContractualObligationsForOperatingLeaseCommitmentsUndiscountedLeaseLiabilityExcessAmount" name="FuturePrincipalContractualObligationsForOperatingLeaseCommitmentsUndiscountedLeaseLiabilityExcessAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="qnst_LiabilitiesRelatedToIndemnificationAgreement" name="LiabilitiesRelatedToIndemnificationAgreement" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="qnst_AccrualForIndemnificationProvisions" name="AccrualForIndemnificationProvisions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="qnst_LettersOfCreditForOperatingLease" name="LettersOfCreditForOperatingLease" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="qnst_PeriodOfCancellationOfLetterOfCreditFromAnnualExpirationDate" name="PeriodOfCancellationOfLetterOfCreditFromAnnualExpirationDate" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="qnst_JulyTwoThousandSeventeenStockRepurchaseProgramMember" name="JulyTwoThousandSeventeenStockRepurchaseProgramMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_TwoThousandTenIncentivePlanMember" name="TwoThousandTenIncentivePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="qnst_DirectorsPlanMember" name="DirectorsPlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
</xsd:schema>
