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

    <schemaVersion>X0603</schemaVersion>

    <submissionType>D/A</submissionType>

    <testOrLive>LIVE</testOrLive>

    <primaryIssuer>
        <cik>0001479678</cik>
        <entityName>SecondMarket Holdings, Inc.</entityName>
        <issuerAddress>
            <street1>26 BROADWAY</street1>
            <street2>12TH FLOOR</street2>
            <city>NEW YORK</city>
            <stateOrCountry>NY</stateOrCountry>
            <zipCode>10004</zipCode>
        </issuerAddress>
        <issuerPhoneNumber>212 668 5920</issuerPhoneNumber>
        <jurisdictionOfInc>DELAWARE</jurisdictionOfInc>
        <issuerPreviousNameList>
            <previousName>RST Group, Inc.</previousName>
        </issuerPreviousNameList>
        <edgarPreviousNameList>
            <value>None</value>
        </edgarPreviousNameList>
        <entityType>Corporation</entityType>
        <yearOfInc>
            <overFiveYears>true</overFiveYears>
        </yearOfInc>
    </primaryIssuer>

    <relatedPersonsList>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Barry</firstName>
                <middleName>E.</middleName>
                <lastName>Silbert</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>26 Broadway, 12th Floor</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10004</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>M.</firstName>
                <middleName>Adam</middleName>
                <lastName>Oliveri</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>26 Broadway, 12th Floor</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10004</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Christopher</firstName>
                <lastName>Chakford</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>26 Broadway, 12th Floor</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10004</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>A.</firstName>
                <middleName>Stuart</middleName>
                <lastName>Donovan</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>26 Broadway, 12th Floor</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10004</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Kevin</firstName>
                <middleName>C.</middleName>
                <lastName>O'Connor</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>26 Broadway, 12th Floor</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10004</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Philip</firstName>
                <middleName>H.</middleName>
                <lastName>Reicherz</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>26 Broadway, 12th Floor</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10004</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Jeremy</firstName>
                <middleName>A.</middleName>
                <lastName>Smith</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>26 Broadway, 12th Floor</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10004</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>John-Paul</firstName>
                <lastName>Teutonico</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>26 Broadway, 12th Floor</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10004</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Charles</firstName>
                <lastName>Almond</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>26 Broadway, 12th Floor</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10004</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>John</firstName>
                <middleName>A.</middleName>
                <lastName>McKenna</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>26 Broadway, 12th Floor</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10004</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Lawrence</firstName>
                <middleName>D.</middleName>
                <lastName>Lenihan</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>1221 Avenue of the Americas 26th Floor</street1>
                <city>New York</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10020</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Mabel</firstName>
                <lastName>Chu Wei Ning</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o 29 F Harbour Centre</street1>
                <street2>25 Harbor Road</street2>
                <city>Hong Kong</city>
                <stateOrCountry>K3</stateOrCountry>
                <zipCode>00000</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
    </relatedPersonsList>

    <offeringData>
        <industryGroup>
            <industryGroupType>Other Banking and Financial Services</industryGroupType>
        </industryGroup>
        <issuerSize>
            <revenueRange>$25,000,001 - $100,000,000</revenueRange>
        </issuerSize>
        <federalExemptionsExclusions>
            <item>06</item>
        </federalExemptionsExclusions>
        <typeOfFiling>
            <newOrAmendment>
                <isAmendment>true</isAmendment>
                <previousAccessionNumber>0001479678-10-000001</previousAccessionNumber>
            </newOrAmendment>
            <dateOfFirstSale>
                <value>2009-12-22</value>
            </dateOfFirstSale>
        </typeOfFiling>
        <durationOfOffering>
            <moreThanOneYear>false</moreThanOneYear>
        </durationOfOffering>
        <typesOfSecuritiesOffered>
            <isEquityType>true</isEquityType>
        </typesOfSecuritiesOffered>
        <businessCombinationTransaction>
            <isBusinessCombinationTransaction>false</isBusinessCombinationTransaction>
            <clarificationOfResponse></clarificationOfResponse>
        </businessCombinationTransaction>
        <minimumInvestmentAccepted>0</minimumInvestmentAccepted>
        <salesCompensationList></salesCompensationList>
        <offeringSalesAmounts>
            <totalOfferingAmount>15000000</totalOfferingAmount>
            <totalAmountSold>15000000</totalAmountSold>
            <totalRemaining>0</totalRemaining>
            <clarificationOfResponse></clarificationOfResponse>
        </offeringSalesAmounts>
        <investors>
            <hasNonAccreditedInvestors>false</hasNonAccreditedInvestors>
            <totalNumberAlreadyInvested>3</totalNumberAlreadyInvested>
        </investors>
        <salesCommissionsFindersFees>
            <salesCommissions>
                <dollarAmount>0</dollarAmount>
            </salesCommissions>
            <findersFees>
                <dollarAmount>0</dollarAmount>
            </findersFees>
            <clarificationOfResponse></clarificationOfResponse>
        </salesCommissionsFindersFees>
        <useOfProceeds>
            <grossProceedsUsed>
                <dollarAmount>0</dollarAmount>
            </grossProceedsUsed>
            <clarificationOfResponse></clarificationOfResponse>
        </useOfProceeds>
        <signatureBlock>
            <authorizedRepresentative>false</authorizedRepresentative>
            <signature>
                <issuerName>SecondMarket Holdings, Inc.</issuerName>
                <signatureName>/s/Scott Passet</signatureName>
                <nameOfSigner>Scott Passet</nameOfSigner>
                <signatureTitle>Deputy General Counsel</signatureTitle>
                <signatureDate>2010-04-06</signatureDate>
            </signature>
        </signatureBlock>
    </offeringData>
</edgarSubmission>
