<?xml version="1.0"?>
<edgarSubmission>

    <schemaVersion>X0708</schemaVersion>

    <submissionType>D/A</submissionType>

    <testOrLive>LIVE</testOrLive>

    <primaryIssuer>
        <cik>0001677121</cik>
        <entityName>Aptitude Onshore Partners Fund L.P.</entityName>
        <issuerAddress>
            <street1>C/O APTITUDE PARTNERS FUND GP LLC</street1>
            <street2>925 FOURTH AVENUE, SUITE 3500</street2>
            <city>SEATTLE</city>
            <stateOrCountry>WA</stateOrCountry>
            <stateOrCountryDescription>WASHINGTON</stateOrCountryDescription>
            <zipCode>98104</zipCode>
        </issuerAddress>
        <issuerPhoneNumber>(206) 788-8800</issuerPhoneNumber>
        <jurisdictionOfInc>DELAWARE</jurisdictionOfInc>
        <issuerPreviousNameList>
            <value>None</value>
        </issuerPreviousNameList>
        <edgarPreviousNameList>
            <previousName>Federal Way Partners US Feeder Fund L.P.</previousName>
        </edgarPreviousNameList>
        <entityType>Limited Partnership</entityType>
        <yearOfInc>
            <withinFiveYears>true</withinFiveYears>
            <value>2016</value>
        </yearOfInc>
    </primaryIssuer>

    <relatedPersonsList>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>-</firstName>
                <lastName>Aptitude Partners Fund GP LLC</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>925 FOURTH AVENUE, SUITE 3500</street1>
                <city>Seattle</city>
                <stateOrCountry>WA</stateOrCountry>
                <stateOrCountryDescription>WASHINGTON</stateOrCountryDescription>
                <zipCode>98104</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>General Partner</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>-</firstName>
                <lastName>Aptitude Investment Management LP</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>925 FOURTH AVENUE, SUITE 3500</street1>
                <city>Seattle</city>
                <stateOrCountry>WA</stateOrCountry>
                <stateOrCountryDescription>WASHINGTON</stateOrCountryDescription>
                <zipCode>98104</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Promoter</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Investment Manager</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Salim</firstName>
                <lastName>Shariff</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o Aptitude Partners Fund GP LLC</street1>
                <street2>925 FOURTH AVENUE, SUITE 3500</street2>
                <city>Seattle</city>
                <stateOrCountry>WA</stateOrCountry>
                <stateOrCountryDescription>WASHINGTON</stateOrCountryDescription>
                <zipCode>98104</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>President and Chief Investment Officer of the Investment Manager</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Jeffrey</firstName>
                <lastName>Klein</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o Aptitude Partners Fund GP LLC</street1>
                <street2>925 FOURTH AVENUE, SUITE 3500</street2>
                <city>Seattle</city>
                <stateOrCountry>WA</stateOrCountry>
                <stateOrCountryDescription>WASHINGTON</stateOrCountryDescription>
                <zipCode>98104</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Chief Executive Officer and Deputy Chief Investment Officer of the Investment Manager</relationshipClarification>
        </relatedPersonInfo>
    </relatedPersonsList>

    <offeringData>
        <industryGroup>
            <industryGroupType>Pooled Investment Fund</industryGroupType>
            <investmentFundInfo>
                <investmentFundType>Hedge Fund</investmentFundType>
                <is40Act>false</is40Act>
            </investmentFundInfo>
        </industryGroup>
        <issuerSize>
            <aggregateNetAssetValueRange>Decline to Disclose</aggregateNetAssetValueRange>
        </issuerSize>
        <federalExemptionsExclusions>
            <item>06b</item>
            <item>3C</item>
            <item>3C.1</item>
        </federalExemptionsExclusions>
        <typeOfFiling>
            <newOrAmendment>
                <isAmendment>true</isAmendment>
                <previousAccessionNumber>0000902664-17-002910</previousAccessionNumber>
            </newOrAmendment>
            <dateOfFirstSale>
                <value>2016-07-01</value>
            </dateOfFirstSale>
        </typeOfFiling>
        <durationOfOffering>
            <moreThanOneYear>true</moreThanOneYear>
        </durationOfOffering>
        <typesOfSecuritiesOffered>
            <isEquityType>true</isEquityType>
            <isPooledInvestmentFundType>true</isPooledInvestmentFundType>
        </typesOfSecuritiesOffered>
        <businessCombinationTransaction>
            <isBusinessCombinationTransaction>false</isBusinessCombinationTransaction>
        </businessCombinationTransaction>
        <minimumInvestmentAccepted>0</minimumInvestmentAccepted>
        <salesCompensationList></salesCompensationList>
        <offeringSalesAmounts>
            <totalOfferingAmount>Indefinite</totalOfferingAmount>
            <totalAmountSold>76438607</totalAmountSold>
            <totalRemaining>Indefinite</totalRemaining>
        </offeringSalesAmounts>
        <investors>
            <hasNonAccreditedInvestors>false</hasNonAccreditedInvestors>
            <totalNumberAlreadyInvested>13</totalNumberAlreadyInvested>
        </investors>
        <salesCommissionsFindersFees>
            <salesCommissions>
                <dollarAmount>0</dollarAmount>
            </salesCommissions>
            <findersFees>
                <dollarAmount>0</dollarAmount>
            </findersFees>
            <clarificationOfResponse></clarificationOfResponse>
        </salesCommissionsFindersFees>
        <useOfProceeds>
            <grossProceedsUsed>
                <dollarAmount>0</dollarAmount>
            </grossProceedsUsed>
            <clarificationOfResponse>The fund charges a management fee that is described in the fund's offering documents.</clarificationOfResponse>
        </useOfProceeds>
        <signatureBlock>
            <authorizedRepresentative>false</authorizedRepresentative>
            <signature>
                <issuerName>Aptitude Onshore Partners Fund L.P.</issuerName>
                <signatureName>/s/ Linda Colwell</signatureName>
                <nameOfSigner>Linda Colwell</nameOfSigner>
                <signatureTitle>General Counsel and CCO of the General Partner</signatureTitle>
                <signatureDate>2018-07-13</signatureDate>
            </signature>
        </signatureBlock>
    </offeringData>
</edgarSubmission>
