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

    <schemaVersion>X0204</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2011-08-10</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000907686</issuerCik>
        <issuerName>CMSF Corp</issuerName>
        <issuerTradingSymbol>CMSF</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001528184</rptOwnerCik>
            <rptOwnerName>Fricano Glenn</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>95 CHURCH AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ISLIP</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>11751</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>398797152</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes></footnotes>

    <remarks>Glenn Fricano is currently holding approximatly 398,797,152 of which approximately 113,050,000 shares are to be transferred to Mr. Stuart M. Sieger only if and when transfer of the same will not cause Mr. Sieger's ownership to exceed 10% of the issued and outstanding Common Stock of the Company.</remarks>

    <ownerSignature>
        <signatureName>/s/ Glenn Fricano</signatureName>
        <signatureDate>2011-08-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
