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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-03-27</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001456772</issuerCik>
        <issuerName>Government Properties Income Trust</issuerName>
        <issuerTradingSymbol>NYSE: GOV</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001241559</rptOwnerCik>
            <rptOwnerName>PORTNOY BARRY M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O REIT MANAGEMENT &amp; RESEARCH LLC</rptOwnerStreet1>
            <rptOwnerStreet2>TWO NEWTON PL., 255 WASH. ST., STE. 300</rptOwnerStreet2>
            <rptOwnerCity>NEWTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02458</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares of Beneficial Interest</value>
            </securityTitle>
            <transactionDate>
                <value>2013-03-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>11126</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>25.42</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>41911.802</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">These shares were issued pursuant to a business management agreement between the Issuer and Reit Management &amp; Research LLC (&quot;RMR&quot;) of which Mr. Portnoy is a director and majority beneficial owner. Mr. Portnoy purchased these shares from RMR upon their issuance.  Such transfers were exempt from Section 16 of the Securities Exchange Act of 1934, as amended, pursuant to Rule 16a-13 thereunder.</footnote>
        <footnote id="F2">In accordance with the business management agreement referred to above, certain historical share price information was used to determine the number of common shares of beneficial interest paid to RMR.  The per share price amount listed above is the closing sale price of the Issuer's common shares of beneficial interest on the New York Stock Exchange on March 27, 2013, when the shares were issued and purchased.</footnote>
        <footnote id="F3">Includes 2,135.989 shares acquired under the Government Properties Income Trust Dividend Reinvestment Plan since the last Section 16 filing by Mr. Portnoy.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Barry M. Portnoy</signatureName>
        <signatureDate>2013-03-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
