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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 CECIRzDxGre+1rCLvCgmcXFKzqYZZ9+3Lvy51WUpTTPYZtqfh4S+waK2NWJ08d3t
 r/xNp+6Qrhcx0rFBo6fnww==

<SEC-DOCUMENT>0001247342-10-000018.txt : 20100805
<SEC-HEADER>0001247342-10-000018.hdr.sgml : 20100805
<ACCEPTANCE-DATETIME>20100805121535
ACCESSION NUMBER:		0001247342-10-000018
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100804
FILED AS OF DATE:		20100805
DATE AS OF CHANGE:		20100805

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MacKenzie William R
		CENTRAL INDEX KEY:			0001474877

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-23695
		FILM NUMBER:		10993441

	MAIL ADDRESS:	
		STREET 1:		160 WASHINGTON STREET
		CITY:			BROOKLINE
		STATE:			MA
		ZIP:			02445

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			BROOKLINE BANCORP INC
		CENTRAL INDEX KEY:			0001049782
		STANDARD INDUSTRIAL CLASSIFICATION:	SAVINGS INSTITUTION, FEDERALLY CHARTERED [6035]
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		160 WASHINGTON STREET
		CITY:			BROOKLINE
		STATE:			MA
		ZIP:			02147
		BUSINESS PHONE:		6177303500

	MAIL ADDRESS:	
		STREET 1:		160 WASHINGTON ST
		CITY:			BROOKLINE
		STATE:			MA
		ZIP:			02147
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-08-04</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001049782</issuerCik>
        <issuerName>BROOKLINE BANCORP INC</issuerName>
        <issuerTradingSymbol>brkl</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001474877</rptOwnerCik>
            <rptOwnerName>MacKenzie William R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>160 WASHINGTON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BROOKLINE</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02445</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Senior vice president</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-08-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>9.62</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7957</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">These shares were awarded under the Company's 2003 Recognition and Retention Plan. The shares vest on August 4, 2012.</footnote>
        <footnote id="F2">Includes 1,088 shares awarded through the ESOP as of December 31, 2009 not required to be reported pursuant to Section 16 of the Securities and Exchange Act of 1934.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Paul R. Bechet, Power of Attorney</signatureName>
        <signatureDate>2010-08-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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