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

    <schemaVersion>X0708</schemaVersion>

    <submissionType>D</submissionType>

    <testOrLive>LIVE</testOrLive>

    <primaryIssuer>
        <cik>0001901856</cik>
        <entityName>Flatiron HoldCo Inc.</entityName>
        <issuerAddress>
            <street1>745 FIFTH AVENUE</street1>
            <city>NEW YORK</city>
            <stateOrCountry>NY</stateOrCountry>
            <stateOrCountryDescription>NEW YORK</stateOrCountryDescription>
            <zipCode>10151</zipCode>
        </issuerAddress>
        <issuerPhoneNumber>720-256-5542</issuerPhoneNumber>
        <jurisdictionOfInc>DELAWARE</jurisdictionOfInc>
        <issuerPreviousNameList>
            <value>None</value>
        </issuerPreviousNameList>
        <edgarPreviousNameList>
            <value>None</value>
        </edgarPreviousNameList>
        <entityType>Corporation</entityType>
        <yearOfInc>
            <withinFiveYears>true</withinFiveYears>
            <value>2021</value>
        </yearOfInc>
    </primaryIssuer>

    <relatedPersonsList>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Jeremy</firstName>
                <lastName>Rudel</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>5400 Airport Road, Suite 300</street1>
                <city>Boulder</city>
                <stateOrCountry>CO</stateOrCountry>
                <stateOrCountryDescription>COLORADO</stateOrCountryDescription>
                <zipCode>80301</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Chris</firstName>
                <lastName>James</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>5400 Airport Road, Suite 300</street1>
                <city>Boulder</city>
                <stateOrCountry>CO</stateOrCountry>
                <stateOrCountryDescription>COLORADO</stateOrCountryDescription>
                <zipCode>80301</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Dean</firstName>
                <lastName>Leffingwell</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>5360 Cypress Drive</street1>
                <city>Boulder</city>
                <stateOrCountry>CO</stateOrCountry>
                <stateOrCountryDescription>COLORADO</stateOrCountryDescription>
                <zipCode>80303</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Scott</firstName>
                <lastName>VanHoy</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>590 Madison Ave.</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <stateOrCountryDescription>NEW YORK</stateOrCountryDescription>
                <zipCode>10022</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Antonin</firstName>
                <lastName>Marcus</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>745 Fifth Avenue</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <stateOrCountryDescription>NEW YORK</stateOrCountryDescription>
                <zipCode>10151</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Sarah</firstName>
                <lastName>Sperry</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>745 Fifth Avenue</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <stateOrCountryDescription>NEW YORK</stateOrCountryDescription>
                <zipCode>10151</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Marc</firstName>
                <lastName>Frappier</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>745 Fifth Avenue</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <stateOrCountryDescription>NEW YORK</stateOrCountryDescription>
                <zipCode>10151</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Antonin</firstName>
                <lastName>de Margerie</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>745 Fifth Avenue</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <stateOrCountryDescription>NEW YORK</stateOrCountryDescription>
                <zipCode>10151</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Domitille</firstName>
                <lastName>Doat</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>745 Fifth Avenue</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <stateOrCountryDescription>NEW YORK</stateOrCountryDescription>
                <zipCode>10151</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Vivianne</firstName>
                <lastName>Akriche</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>745 Fifth Avenue</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <stateOrCountryDescription>NEW YORK</stateOrCountryDescription>
                <zipCode>10151</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
        </relatedPersonInfo>
    </relatedPersonsList>

    <offeringData>
        <industryGroup>
            <industryGroupType>Business Services</industryGroupType>
        </industryGroup>
        <issuerSize>
            <revenueRange>Decline to Disclose</revenueRange>
        </issuerSize>
        <federalExemptionsExclusions>
            <item>06b</item>
        </federalExemptionsExclusions>
        <typeOfFiling>
            <newOrAmendment>
                <isAmendment>false</isAmendment>
            </newOrAmendment>
            <dateOfFirstSale>
                <value>2021-12-16</value>
            </dateOfFirstSale>
        </typeOfFiling>
        <durationOfOffering>
            <moreThanOneYear>false</moreThanOneYear>
        </durationOfOffering>
        <typesOfSecuritiesOffered>
            <isEquityType>true</isEquityType>
        </typesOfSecuritiesOffered>
        <businessCombinationTransaction>
            <isBusinessCombinationTransaction>false</isBusinessCombinationTransaction>
        </businessCombinationTransaction>
        <minimumInvestmentAccepted>0</minimumInvestmentAccepted>
        <salesCompensationList></salesCompensationList>
        <offeringSalesAmounts>
            <totalOfferingAmount>11945748</totalOfferingAmount>
            <totalAmountSold>11945748</totalAmountSold>
            <totalRemaining>0</totalRemaining>
        </offeringSalesAmounts>
        <investors>
            <hasNonAccreditedInvestors>false</hasNonAccreditedInvestors>
            <totalNumberAlreadyInvested>25</totalNumberAlreadyInvested>
        </investors>
        <salesCommissionsFindersFees>
            <salesCommissions>
                <dollarAmount>0</dollarAmount>
            </salesCommissions>
            <findersFees>
                <dollarAmount>0</dollarAmount>
            </findersFees>
        </salesCommissionsFindersFees>
        <useOfProceeds>
            <grossProceedsUsed>
                <dollarAmount>0</dollarAmount>
            </grossProceedsUsed>
        </useOfProceeds>
        <signatureBlock>
            <authorizedRepresentative>false</authorizedRepresentative>
            <signature>
                <issuerName>Flatiron HoldCo Inc.</issuerName>
                <signatureName>/s/ Jeremy Rudel</signatureName>
                <nameOfSigner>Jeremy Rudel</nameOfSigner>
                <signatureTitle>Vice President, Treasurer and Secretary</signatureTitle>
                <signatureDate>2021-12-23</signatureDate>
            </signature>
        </signatureBlock>
    </offeringData>
</edgarSubmission>
