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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-03-07</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001720893</issuerCik>
        <issuerName>BioXcel Therapeutics, Inc.</issuerName>
        <issuerTradingSymbol>BTAI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001653967</rptOwnerCik>
            <rptOwnerName>Votruba Michal</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BIOXCEL THERAPEUTICS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>555 LONG WARF DRIVE</rptOwnerStreet2>
            <rptOwnerCity>NEW HAVEN</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06511</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>7.91</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2019-03-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>7.91</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2029-03-07</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10000</value>
                    <footnoteId id="F2"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The shares underlying this stock option vest as follows: one-third on each of 3/7/2020, 3/7/2021 and 3/7/2022, subject to the Reporting Person's continuous service to the Issuer through such dates.</footnote>
        <footnote id="F2">The Reporting Person immediately and automatically assigned these stock options to RSJ Investments SICAV a.s. (&quot;RSJ&quot;) pursuant to the policies of RSJ regarding stock ownership by its employees, as documented by an Agreement between the Reporting Person and RSJ. The Reporting Person is serving on the Board of the Issuer with the permission of RSJ.</footnote>
    </footnotes>

    <remarks>The Reporting Person does not beneficially own any non-derivative securities.</remarks>

    <ownerSignature>
        <signatureName>/s/ Michal Votruba</signatureName>
        <signatureDate>2019-03-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
