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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-08-07</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001080056</issuerCik>
        <issuerName>THESTREET, INC.</issuerName>
        <issuerTradingSymbol>TST</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001289134</rptOwnerCik>
            <rptOwnerName>Rendino Kevin</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>7N WILLOW STREET</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 4B</rptOwnerStreet2>
            <rptOwnerCity>MONTCLAIR</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07042</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $.01 per share</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2019-08-07</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>6474</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $.01 per share</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2019-08-07</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>821521</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote.</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On June 11, 2019, TheStreet, Inc. (the &quot;Company&quot;) entered into an Agreement and Plan of Merger, as amended, (the &quot;Merger Agreement&quot;) with TheMaven, Inc. (the &quot;Parent&quot;) and a wholly owned subsidiary of the Parent (the &quot;Merger Sub&quot;). On August 7, 2019, pursuant to the Merger Agreement, Merger Sub merged with and into the Company, and the Company continued as the surviving corporation and as a wholly owned subsidiary of Parent (the &quot;Merger&quot;).</footnote>
        <footnote id="F2">Pursuant to the Merger Agreement, all shares of Company common stock were cancelled and exchanged for merger consideration of $3.09183364 per share in the Merger, plus one contractual contingent value right per share (&quot;CVR&quot;) (as defined in the Merger Agreement).</footnote>
        <footnote id="F3">363,636 of these shares of Common Stock were purchased by 180 Degree Capital Corp. (&quot;180&quot;) and 350,000 of these shares were purchased by TheStreet SPV Series-a series of 180 Degree Capital Management, LLC (&quot;TST SPV&quot;) on November 10, 2017, in a private placement pursuant to a Securities Purchase Agreement between 180, TST SPV and TheStreet, Inc. (&quot;TST&quot;). The remaining 100,000 shares of Common Stock were purchased by 180 in open market transactions through April to June 2017, prior to Mr. Rendino becoming a Reporting Person. The remaining 7,885 shares were purchased/received through exercise of options and vesting of restricted stock.</footnote>
        <footnote id="F4">471,521 of these shares of Common Stock are owned by 180. 350,000 of these shares of Common Stock are owned by TST SPV. 180 is the Managing Member and Investment Manager of TST SPV. Mr. Rendino is Chief Executive Officer and Portfolio Manager of 180 Degree Capital Corp. and has shared voting and dispositive control over the shares of TST owned by 180 and TST SPV through his position at 180. Mr. Rendino disclaims beneficial ownership of these shares.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Kevin Rendino</signatureName>
        <signatureDate>2019-08-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
