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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2017-05-10</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001444363</issuerCik>
        <issuerName>GAIN Capital Holdings, Inc.</issuerName>
        <issuerTradingSymbol>GCAP</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001707089</rptOwnerCik>
            <rptOwnerName>IPGL Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>CITYPOINT LEVEL 28</rptOwnerStreet1>
            <rptOwnerStreet2>ONE ROPEMAKER STREET</rptOwnerStreet2>
            <rptOwnerCity>LONDON</rptOwnerCity>
            <rptOwnerState>X0</rptOwnerState>
            <rptOwnerZipCode>EC2Y 9AW</rptOwnerZipCode>
            <rptOwnerStateDescription>UNITED KINGDOM</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001665705</rptOwnerCik>
            <rptOwnerName>FOX &amp; TROT LTD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>CITYPOINT LEVEL 28</rptOwnerStreet1>
            <rptOwnerStreet2>ONE ROPEMAKER STREET</rptOwnerStreet2>
            <rptOwnerCity>LONDON</rptOwnerCity>
            <rptOwnerState>X0</rptOwnerState>
            <rptOwnerZipCode>EC2Y 9AW</rptOwnerZipCode>
            <rptOwnerStateDescription>UNITED KINGDOM</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.00001 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>150050</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.00001 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4629950</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On May 10, 2017, the Issuer filed a Quarterly Report on Form 10-Q disclosing a new number of outstanding shares of common stock. As a result of the new number of outstanding shares, the reporting persons now beneficially own more than 10% of the Issuer's outstanding common stock.</footnote>
        <footnote id="F2">The 150,050 shares of common stock are held of record by IPGL Limited (&quot;IPGL&quot;). David Jeremy Courtenay-Stamp, David Gelber, Mark William Lane Richards, Michael Patrick Spencer and Michael Alan Spencer are the directors of IPGL, and have the power, acting by majority vote, to vote or dispose of shares directly held by IPGL. Messrs. Courtenay-Stamp, Gelber, Richards, Spencer and Spencer each hereby disclaims any beneficial ownership of any shares directly or indirectly held by IPGL, except to the extent of their pecuniary interest therein.</footnote>
        <footnote id="F3">The 4,629,950 shares of common stock are held of record by Fox &amp; Trot Limited (&quot;F&amp;T&quot;). IPGL, the 100% owner of F&amp;T, may be deemed to beneficially own the reported shares. Frederick Morton, Mark William Lane Richards and Tom Scarborough are the directors of F&amp;T, and act at the direction of the directors of IPGL to vote or dispose of shares directly held by F&amp;T, except in certain limited circumstances where they have the power, acting by majority vote, to vote or dispose of shares directly held by F&amp;T. Messrs. Morton, Richards and Scarborough each hereby disclaims any beneficial ownership of any shares directly held by F&amp;T, except to the extent of their pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>IPGL Limited, by /s/ Mark William Lane Richards, its director and chief executive officer</signatureName>
        <signatureDate>2017-05-19</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Fox &amp; Trot Limited, by /s/ Mark William Lane Richards, its director</signatureName>
        <signatureDate>2017-05-19</signatureDate>
    </ownerSignature>
</ownershipDocument>
