<?xml version="1.0"?>

<ownershipDocument>

    <documentType>4</documentType>

    <periodOfReport>2003-06-30</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000929454</issuerCik>
        <issuerName>GLENBOROUGH REALTY TRUST INC</issuerName>
        <issuerTradingSymbol>glb</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001007544</rptOwnerCik>
            <rptOwnerName>BATINOVICH ROBERT</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chairman and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Preferred Stock</value>
        </securityTitle>
        <transactionDate>
            <value>2003-06-30</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>J</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
            <footnoteId id="F1"/>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>2680</value>
            </transactionShares>
            <transactionValue>
                <value>0</value>
                <footnoteId id="F1"/>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>D</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>9499</value>
                <footnoteId id="F2"/>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>via Glenborough Partners</value>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock</value>
        </securityTitle>
        <transactionDate>
            <value>2003-06-30</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>J</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
            <footnoteId id="F1"/>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>11658</value>
            </transactionShares>
            <transactionValue>
                <value>0</value>
                <footnoteId id="F1"/>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>D</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>41318</value>
                <footnoteId id="F2"/>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>via Glenborough Partners</value>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <derivativeSecurity>
        <securityTitle>
            <value>OP Units</value>
        </securityTitle>
        <conversionOrExercisePrice>
            <value>0</value>
            <footnoteId id="F3"/>
        </conversionOrExercisePrice>
        <transactionDate>
            <value>2003-06-30</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>J</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
            <footnoteId id="F1"/>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>52357</value>
            </transactionShares>
            <transactionValue>
                <value>0</value>
                <footnoteId id="F4"/>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>D</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <exerciseDate>
            <value>2003-06-30</value>
            <footnoteId id="F3"/>
        </exerciseDate>
        <expirationDate>
            <value>2003-06-30</value>
            <footnoteId id="F4"/>
        </expirationDate>
        <underlyingSecurity>
            <underlyingSecurityTitle>
                <value>Common Stock</value>
            </underlyingSecurityTitle>
            <underlyingSecurityShares>
                <value>52357</value>
            </underlyingSecurityShares>
        </underlyingSecurity>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>185557</value>
                <footnoteId id="F4"/>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>via Glenborough Partners</value>
            </natureOfOwnership>
        </ownershipNature>
    </derivativeSecurity>

    <footnotes>
        <footnote id="F1">This decrease in securities of the Issuer indirectly owned by the reporting person did not involve a transfer of securities of the Issuer. The reporting person is an investor in Glenborough Partners (GPA), a partnership that owns securities of the Issuer, as well as substantial other assets. In January 2003, the reporting person acquired additional interests in GPA, which increased the reporting person's pro rata indirect interest in securities of the Issuer held by GPA, and which was reported on Form 4 as of 1/14/03 as an acquisition of securities of the Issuer. As indicated in the previous Form 4, the reporting person has now disposed of some of those newly acquired interests in GPA. Such disposition reduced the reporting person's pro rata indirect interest in securities of the Issuer held by GPA; such reduction is now reported on Form 4 as a disposition of securities of the Issuer, even though there has been no transfer of interests in securities of the Issuer.</footnote>
        <footnote id="F2">Glenborough Partners is a partnership in which the reporting person holds an interest.  Represents the reporting person's beneficial interest in securities of the Issuer held or acquired (or disposed of, as the case may be) by Glenborough Partners.  No consideration was paid (or received, as the case may be) by the reporting person in connection with such acquisition (or disposition, as the case may be).</footnote>
        <footnote id="F3">The OP Units are not convertible or exercisable, but may be redeemed for either cash or, at Issuer's option, in exchange for a number of shares of Issuer's common stock equal to the number of OP Units being redeemed.</footnote>
        <footnote id="F4">Represents the reporting person's portion of the shares of common stock of the Issuer that would be acquired by Glenborough Partners (a partnership in which the reporting person holds an interest), if Glenborough Partners exercises its option to redeem (&quot;Redemption Rights&quot;) certain operating partnership units (&quot;OP Units&quot;) in Glenborough Properties, L.P. (the &quot;Operating Partnership&quot;), and the Issuer, as general partner of the Operating Partnership, in turn elects to acquire such OP Units in exchange for shares sof the Issuer's common stock, rather than for cash.  The number of shares issued in such case would be equal to the number of OP Units redeemed.  Beneficial ownership of Glenborough Partners' OP Units is indirectly attributable to the reporting person by virtue of the reporting person's partnership interest in Glenborough Partners.  The Redemption Rights expire on December 31, 2095, the expiration of the term of the Operating Partnership.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Robert Batinovich</signatureName>
        <signatureDate>2003-06-30</signatureDate>
    </ownerSignature>

</ownershipDocument>

