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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-06-30</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001465128</issuerCik>
        <issuerName>STARWOOD PROPERTY TRUST, INC.</issuerName>
        <issuerTradingSymbol>STWD</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001034657</rptOwnerCik>
            <rptOwnerName>STERNLICHT BARRY S</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O STARWOOD PROPERTY TRUST, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>591 WEST PUTNAM AVENUE</rptOwnerStreet2>
            <rptOwnerCity>GREENWICH</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06830</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO, Chairman of Board</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-06-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>342528</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1271527</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By controlled entities</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4073163</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2015-06-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>342528</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>342528</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1900780</value>
                    <footnoteId id="F6"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By controlled entities</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On June 30, 2015, SPT Management, LLC, the issuer's external manager (the &quot;Manager&quot;), acquired 286,277 shares of the issuer's common stock in connection with the vesting of (i) 72,916 restricted stock units originally granted to the Manager on October 10, 2012 as an award under the Starwood Property Trust, Inc. Manager Equity Plan (the &quot;2012 RSUs&quot;), (ii) 166,667 restricted stock units originally granted to the Manager on January 2, 2014 as an award under the Starwood Property Trust, Inc. Manager Equity Plan (the &quot;2014 RSUs&quot;), (iii) 46,695 restricted stock units originally granted to the Manager on January 31, 2014 (continued in footnote 2 below)</footnote>
        <footnote id="F2">as an award under the Starwood Property Trust, Inc. Manager Equity Plan in connection with the distribution of common shares of Starwood Waypoint Residential Trust to holders of shares of the issuer's common stock on January 24, 2014 (the &quot;Distribution RSUs&quot;) and (iv) 56,250 restricted stock units originally granted to the Manager on May 18, 2015 as an award under the Starwood Property Trust, Inc. Manager Equity Plan (the &quot;2015 RSUs&quot;).</footnote>
        <footnote id="F3">The remaining 2012 RSUs, 2014 RSUs and 2015 RSUs will vest ratably in quarterly installments through September 30, 2015, December 31, 2016 and March 31, 2018, respectively, in each case subject to the Manager's continued service as the issuer's external manager. The remaining Distribution RSUs will vest ratably in quarterly installments on the same schedule applicable to the 2012 RSUs and 2014 RSUs held by the Manager as of the grant date, subject to the Manager's continued service as the issuer's external manager. In each case as such restricted stock units vest, the award will be settled in shares of the issuer's common stock promptly, but in no event later than 30 days, following the applicable quarterly vesting date.</footnote>
        <footnote id="F4">Represents shares held by the Manager and SFIP, L.P. (&quot;SFIP&quot;). Starwood Capital Group Global, L.P. (&quot;SCGG&quot;) is the sole member of the Manager.  Mr. Sternlicht is the controlling partner of each of SFIP and SCGG.</footnote>
        <footnote id="F5">Each restricted stock unit represents a contingent right to receive one share of the issuer's common stock.</footnote>
        <footnote id="F6">Represents the 875,000 restricted stock units granted to the Manager on October 10, 2012, the 2,000,000 restricted stock units granted to the Manager on January 2, 2014, the 489,281 restricted stock units granted to the Manager on January 31, 2014 and the 675,000 restricted stock units granted to the Manager on May 18, 2015, less those restricted stock units that have already vested and been converted into shares of common stock.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Barry S. Sternlicht</signatureName>
        <signatureDate>2015-07-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
