<?xml version="1.0" encoding="UTF-8"?>
<edgarSubmission xmlns="http://www.sec.gov/edgar/ncen" xmlns:com="http://www.sec.gov/edgar/common">
  <schemaVersion>X0404</schemaVersion>
  <headerData>
    <submissionType>N-CEN</submissionType>
    <filerInfo>
      <liveTestFlag>LIVE</liveTestFlag>
      <filer>
        <issuerCredentials>
          <cik>0001976685</cik>
          <ccc>XXXXXXXX</ccc>
        </issuerCredentials>
        <fileNumber>811-23874</fileNumber>
      </filer>
      <flags>
        <returnCopyFlag>false</returnCopyFlag>
        <overrideInternetFlag>false</overrideInternetFlag>
        <confirmingCopyFlag>false</confirmingCopyFlag>
      </flags>
      <investmentCompanyType>N-2</investmentCompanyType>
    </filerInfo>
  </headerData>
  <formData>
    <generalInfo reportEndingPeriod="2025-03-31" isReportPeriodLt12="N"/>
    <registrantInfo>
      <registrantFullName>Institutional Investment Strategy Fund</registrantFullName>
      <investmentCompFileNo>811-23874</investmentCompFileNo>
      <registrantCik>0001976685</registrantCik>
      <registrantLei>529900E6KJXM64NM1131</registrantLei>
      <registrantstreet1>2261 Market Street #5190</registrantstreet1>
      <registrantcity>San Francisco</registrantcity>
      <registrantzipCode>94114</registrantzipCode>
      <registrantstate>US-CA</registrantstate>
      <registrantcountry>US</registrantcountry>
      <registrantphoneNumber>800-535-7096</registrantphoneNumber>
      <websites>
        <website webpage="buenacapital.com"/>
      </websites>
      <locationBooksRecords>
        <locationBooksRecord>
          <officeName>Fifth Third Bank, National Association</officeName>
          <officeAddress1>38 Fountain Square Plaza MD 1090X9</officeAddress1>
          <officeCity>Cincinnati</officeCity>
          <officeStateCountry officeCountry="US" officeState="US-OH"/>
          <officeRecordsZipCode>45202</officeRecordsZipCode>
          <officePhone>000-0000</officePhone>
          <booksRecordsDesc>Records of the Fund's securities and cash</booksRecordsDesc>
        </locationBooksRecord>
      </locationBooksRecords>
      <isRegistrantFirstFiling>N</isRegistrantFirstFiling>
      <isRegistrantLastFiling>N</isRegistrantLastFiling>
      <isRegistrantFamilyInvComp>N</isRegistrantFamilyInvComp>
      <registrantClassificationType>N-2</registrantClassificationType>
      <isSecuritiesActRegistration>Y</isSecuritiesActRegistration>
      <directors>
        <director>
          <directorName>Wenwen McElhoe</directorName>
          <crdNumber>007803585</crdNumber>
          <isDirectorInterestedPerson>Y</isDirectorInterestedPerson>
          <fileNumbers>
            <fileNumberInfo fileNumber="N/A"/>
          </fileNumbers>
        </director>
        <director>
          <directorName>Brian O'Neil</directorName>
          <crdNumber>N/A</crdNumber>
          <isDirectorInterestedPerson>N</isDirectorInterestedPerson>
          <fileNumbers>
            <fileNumberInfo fileNumber="N/A"/>
          </fileNumbers>
        </director>
        <director>
          <directorName>Bharath Potti</directorName>
          <crdNumber>N/A</crdNumber>
          <isDirectorInterestedPerson>N</isDirectorInterestedPerson>
          <fileNumbers>
            <fileNumberInfo fileNumber="N/A"/>
          </fileNumbers>
        </director>
        <director>
          <directorName>Ross Weiner</directorName>
          <crdNumber>N/A</crdNumber>
          <isDirectorInterestedPerson>N</isDirectorInterestedPerson>
          <fileNumbers>
            <fileNumberInfo fileNumber="N/A"/>
          </fileNumbers>
        </director>
      </directors>
      <chiefComplianceOfficers>
        <chiefComplianceOfficer>
          <ccoName>Peter R. Guarino</ccoName>
          <crdNumber>N/A</crdNumber>
          <ccoStreet1>9 Terison Drive Suite 100</ccoStreet1>
          <ccoCity>Falmouth</ccoCity>
          <ccoStateCountry ccoCountry="US" ccoState="US-ME"/>
          <ccoZipCode>04105</ccoZipCode>
          <ccoPhone>XXXXXX</ccoPhone>
          <isCcoChangedSinceLastFiling>N</isCcoChangedSinceLastFiling>
          <ccoEmployers>
            <ccoEmployer ccoEmployerName="Compliance4, LLC" ccoEmployerId="82-5137381"/>
          </ccoEmployers>
        </chiefComplianceOfficer>
      </chiefComplianceOfficers>
      <isRegistrantSubmittedMatter>N</isRegistrantSubmittedMatter>
      <isPreviousLegalProceeding>N</isPreviousLegalProceeding>
      <isPreviousProceedingTerminated>N</isPreviousProceedingTerminated>
      <isClaimFiled>N</isClaimFiled>
      <coveredByInsurancePolicy isCoveredByInsurancePolicy="Y" isClaimFiledDuringPeriod="N"/>
      <isFinancialSupportDuringPeriod>N</isFinancialSupportDuringPeriod>
      <releaseNumbers isExemptionFromAct="Y">
        <releaseNumberInfo releaseNumber="IC-35398"/>
      </releaseNumbers>
      <isUnderwriterHiredOrTerminated>N</isUnderwriterHiredOrTerminated>
      <publicAccountants>
        <publicAccountant>
          <publicAccountantName>Cohen &amp; Company, Ltd.</publicAccountantName>
          <pcaobNumber>145</pcaobNumber>
          <publicAccountantLei>N/A</publicAccountantLei>
          <publicAccountantStateCountry publicAccountantCountry="US" publicAccountantState="US-PA"/>
        </publicAccountant>
      </publicAccountants>
      <isPublicAccountantChanged>N</isPublicAccountantChanged>
      <isMaterialWeakness>N</isMaterialWeakness>
      <isOpinionOffered>N</isOpinionOffered>
      <isMaterialChange>N</isMaterialChange>
      <isAccountingPrincipleChange>N</isAccountingPrincipleChange>
      <isPaymentErrorInNetAssetValue>N</isPaymentErrorInNetAssetValue>
      <isPaymentDividend>N</isPaymentDividend>
    </registrantInfo>
    <managementInvestmentQuestionSeriesInfo>
      <managementInvestmentQuestion>
        <mgmtInvFundName>Institutional Investment Strategy Fund</mgmtInvFundName>
        <mgmtInvLei>529900E6KJXM64NM1131</mgmtInvLei>
        <isFirstFilingByFund>N</isFirstFilingByFund>
        <fundTypes>
          <fundType>Interval Fund</fundType>
        </fundTypes>
        <isNonDiversifiedCompany>Y</isNonDiversifiedCompany>
        <isForeignSubsidiary>N</isForeignSubsidiary>
        <isFundSecuritiesLending>N</isFundSecuritiesLending>
        <didFundLendSecurities>N</didFundLendSecurities>
        <paymentToAgentManagerType>N/A</paymentToAgentManagerType>
        <avgPortfolioSecuritiesValue>0.00000000</avgPortfolioSecuritiesValue>
        <netIncomeSecuritiesLending>0.00000000</netIncomeSecuritiesLending>
        <relyOnRuleTypes>
          <relyOnRuleType>Rule 23c-1 (17 CFR 270.23c-1)</relyOnRuleType>
          <relyOnRuleType>Rule 32a-4 (17 CFR 270.32a-4)</relyOnRuleType>
        </relyOnRuleTypes>
        <isExpenseLimitationInPlace>N</isExpenseLimitationInPlace>
        <isExpenseReducedOrWaived>N</isExpenseReducedOrWaived>
        <isFeesWaivedRecoupable>N</isFeesWaivedRecoupable>
        <isExpenseWaivedRecoupable>N</isExpenseWaivedRecoupable>
        <investmentAdvisers>
          <investmentAdviser>
            <investmentAdviserName>Buena Capital Advisors, LLC</investmentAdviserName>
            <investmentAdviserFileNo>801-129430</investmentAdviserFileNo>
            <investmentAdviserCrdNo>000328122</investmentAdviserCrdNo>
            <investmentAdviserLei>N/A</investmentAdviserLei>
            <investmentAdviserStateCountry investmentAdviserState="US-CA" investmentAdviserCountry="US"/>
            <isInvestmentAdviserHired>N</isInvestmentAdviserHired>
          </investmentAdviser>
        </investmentAdvisers>
        <subAdvisers>
          <subAdviser>
            <subAdviserName>Rhumbline Advisors, LP</subAdviserName>
            <subAdviserFileNo>801-40535</subAdviserFileNo>
            <subAdviserCrdNo>000107151</subAdviserCrdNo>
            <subAdviserLei>N/A</subAdviserLei>
            <isSubAdviserAffiliated>N</isSubAdviserAffiliated>
            <subAdviserStateCountry subAdviserState="US-MA" subAdviserCountry="US"/>
            <isSubAdviserHired>N</isSubAdviserHired>
          </subAdviser>
        </subAdvisers>
        <transferAgents>
          <transferAgent>
            <transferAgentName>MUFG Investor Services (US), LLC</transferAgentName>
            <transferAgentFileNo>084-05475</transferAgentFileNo>
            <transferAgentLei>N/A</transferAgentLei>
            <transferAgentStateCountry transferAgentState="US-MD" transferAgentCountry="US"/>
            <isTransferAgentAffiliated>N</isTransferAgentAffiliated>
            <isTransferAgentSubAgent>N</isTransferAgentSubAgent>
          </transferAgent>
        </transferAgents>
        <isTransferAgentHiredOrTerminated>N</isTransferAgentHiredOrTerminated>
        <pricingServices>
          <pricingService>
            <pricingServiceName>ICE Data Services</pricingServiceName>
            <pricingServiceLei>5493000NQ9LYLDBCTL34</pricingServiceLei>
            <pricingServiceStateCountry pricingServiceState="US-NY" pricingServiceCountry="US"/>
            <isPricingServiceAffiliated>N</isPricingServiceAffiliated>
          </pricingService>
        </pricingServices>
        <isPricingServiceHiredOrTerminated>N</isPricingServiceHiredOrTerminated>
        <custodians>
          <custodian>
            <custodianName>Fifth Third Bank, National Association</custodianName>
            <custodianLei>QFROUN1UWUYU0DVIWD51</custodianLei>
            <custodianStateCountry custodianState="US-OH" custodianCountry="US"/>
            <isCustodianAffiliated>N</isCustodianAffiliated>
            <isSubCustodian>N</isSubCustodian>
            <custodyType>Bank - section 17(f)(1) (15 U.S.C. 80a-17(f)(1))</custodyType>
          </custodian>
        </custodians>
        <isCustodianHiredOrTerminated>N</isCustodianHiredOrTerminated>
        <shareholderServicingAgents>
          <shareholderServicingAgent>
            <shareholderServiceAgentName>MUFG Investor Services (US), LLC</shareholderServiceAgentName>
            <shareholderServiceAgentLei>084-05475</shareholderServiceAgentLei>
            <shareholderServiceIdNumberDesc>SEC File Number</shareholderServiceIdNumberDesc>
            <shareholderServiceAgentStateCountry shareholderServiceAgentState="US-MD" shareholderServiceAgentCountry="US"/>
            <isShareholderServiceAgentAffiliated>N</isShareholderServiceAgentAffiliated>
            <isShareholderServiceAgentSubshare>N</isShareholderServiceAgentSubshare>
          </shareholderServicingAgent>
        </shareholderServicingAgents>
        <isShareholderServiceHiredTerminated>N</isShareholderServiceHiredTerminated>
        <admins>
          <admin>
            <adminName>MUFG Investor Services (US), LLC</adminName>
            <adminLei>084-05475</adminLei>
            <idNumberDesc>SEC File Number</idNumberDesc>
            <adminStateCountry adminState="US-MD" adminCountry="US"/>
            <isAdminAffiliated>N</isAdminAffiliated>
            <isAdminSubAdmin>N</isAdminSubAdmin>
          </admin>
        </admins>
        <isAdminHiredOrTerminated>N</isAdminHiredOrTerminated>
        <brokers>
          <broker>
            <brokerName>LOOP CAPITAL MARKETS LLC</brokerName>
            <brokerFileNo>8-50140</brokerFileNo>
            <brokerCrdNo>000043098</brokerCrdNo>
            <brokerLei>254900FPPM2WN90D4786</brokerLei>
            <brokerStateCountry brokerState="US-IL" brokerCountry="US"/>
            <grossCommission>0.90000000</grossCommission>
          </broker>
          <broker>
            <brokerName>WILLIAMS CAPITAL GROU, L.P.</brokerName>
            <brokerFileNo>8-49877</brokerFileNo>
            <brokerCrdNo>000042568</brokerCrdNo>
            <brokerLei>254900VTARX8RAY9QK77</brokerLei>
            <brokerStateCountry brokerState="US-NY" brokerCountry="US"/>
            <grossCommission>9.03000000</grossCommission>
          </broker>
          <broker>
            <brokerName>Instinet, LLC</brokerName>
            <brokerFileNo>8-23669</brokerFileNo>
            <brokerCrdNo>000007897</brokerCrdNo>
            <brokerLei>549300MGMN3RKMU8FT57</brokerLei>
            <brokerStateCountry brokerState="US-NY" brokerCountry="US"/>
            <grossCommission>15.36000000</grossCommission>
          </broker>
          <broker>
            <brokerName>CABRERA CAPITAL MARKETS, LLC</brokerName>
            <brokerFileNo>8-26406</brokerFileNo>
            <brokerCrdNo>000010081</brokerCrdNo>
            <brokerLei>254900BIRJU76JRBK985</brokerLei>
            <brokerStateCountry brokerState="US-IL" brokerCountry="US"/>
            <grossCommission>4.97000000</grossCommission>
          </broker>
          <broker>
            <brokerName>LIQUIDNET, INC.</brokerName>
            <brokerFileNo>8-52461</brokerFileNo>
            <brokerCrdNo>000103987</brokerCrdNo>
            <brokerLei>213800HSKBBO1GCVRG79</brokerLei>
            <brokerStateCountry brokerState="US-NY" brokerCountry="US"/>
            <grossCommission>49.81000000</grossCommission>
          </broker>
          <broker>
            <brokerName>Virtus Americas LLC</brokerName>
            <brokerFileNo>8-68193</brokerFileNo>
            <brokerCrdNo>000149823</brokerCrdNo>
            <brokerLei>549300RA02N3BNSWBV74</brokerLei>
            <brokerStateCountry brokerState="US-DE" brokerCountry="US"/>
            <grossCommission>40.07000000</grossCommission>
          </broker>
        </brokers>
        <aggregateCommission>120.14000000</aggregateCommission>
        <principalTransactions>
          <principalTransaction>
            <principalName>Fifth Third Securities, Inc.</principalName>
            <principalFileNo>8-2428</principalFileNo>
            <principalCrdNo>000000628</principalCrdNo>
            <principalLei>5493003IMO3TYX51WE43</principalLei>
            <principalStateCountry principalState="US-OH" principalCountry="US"/>
            <principalTotalPurchaseSale>2135511.37000000</principalTotalPurchaseSale>
          </principalTransaction>
        </principalTransactions>
        <principalAggregatePurchase>2135511.00000000</principalAggregatePurchase>
        <isBrokerageResearchPayment>N</isBrokerageResearchPayment>
        <mnthlyAvgNetAssets>5894099.03083300</mnthlyAvgNetAssets>
        <dailyAvgNetAssets>0.00000000</dailyAvgNetAssets>
      </managementInvestmentQuestion>
    </managementInvestmentQuestionSeriesInfo>
    <closedEndManagementInvestment>
      <securityRelatedItems>
        <securityRelatedItem>
          <description>Common stock</description>
          <securityClassTitle>Common stock</securityClassTitle>
          <commonStocks>
            <commonStock commonStockExchange="N/A" commonStockTickerSymbol="XIVYX"/>
            <commonStock commonStockExchange="N/A" commonStockTickerSymbol="IVYIX"/>
          </commonStocks>
        </securityRelatedItem>
      </securityRelatedItems>
      <isRightsOffering>N</isRightsOffering>
      <isSecondaryOffering>N</isSecondaryOffering>
      <repurchaseSecurities isRepurchaseSecurity="Y">
        <repurchaseSecurityType>Common stock</repurchaseSecurityType>
      </repurchaseSecurities>
      <isDefaultLongTermDebt>N</isDefaultLongTermDebt>
      <isDividendsInArrears>N</isDividendsInArrears>
      <isSecuritiesModified>N</isSecuritiesModified>
      <managementFee>0.75000000</managementFee>
      <netOperatingExpenses>0.75000000</netOperatingExpenses>
      <marketPricePerShare>N/A</marketPricePerShare>
      <netAssetValuePerShare>10.82000000</netAssetValuePerShare>
    </closedEndManagementInvestment>
    <attachmentsTab>
      <isLegalProceedings>false</isLegalProceedings>
      <isProvisionFinancialSupport>false</isProvisionFinancialSupport>
      <isIPAReportInternalControl>true</isIPAReportInternalControl>
      <isChangeAccPrinciples>false</isChangeAccPrinciples>
      <isInfoRequiredEO>false</isInfoRequiredEO>
      <isOtherInfoRequired>false</isOtherInfoRequired>
      <isMaterialAmendments>false</isMaterialAmendments>
      <isInstDefiningRights>false</isInstDefiningRights>
      <isNewOrAmendedInvAdvContracts>false</isNewOrAmendedInvAdvContracts>
      <isInfoItem405>false</isInfoItem405>
      <isCodeOfEthics>false</isCodeOfEthics>
    </attachmentsTab>
    <signature registrantSignedName="Institutional Investment Strategy Fund" signedDate="2025-06-13" signature="Matthew Pauker" title="Principal Financial Officer"/>
  </formData>
</edgarSubmission>
