<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-07-01</periodOfReport>
    <issuer>
        <issuerCik>0001060021</issuerCik>
        <issuerName>BLACKROCK INC /NY</issuerName>
        <issuerTradingSymbol>BLK</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId>
            <rptOwnerCik>0001210392</rptOwnerCik>
            <rptOwnerName>WAGNER LAWRENCE</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Shares of Class A Common Stock (par value $0.01 per share)</value></securityTitle><transactionDate><value>2003-07-01</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>147</value><footnoteId id="F1"/></transactionShares><transactionValue><value>0</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>6230</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value><footnoteId id="F2"/></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeSecurity><footnotes><footnote id="F1">Shares acquired pursuant to the BlackRock, Inc. Nonemployees Directors Stock Compensation Plan.</footnote><footnote id="F2">Lawrence M. Wagner and his wife jointly own 1,544 shares of BlackRock, Inc., including the current issuance of 147 shares pursuant to the BlackRock, Inc. Nonemployee Directors Stock Compensation Plan. Mr. Wagner additionally owns 4,686 shares of BlackRock, Inc. individually, as follows: through a Keogh account Mr. Wagner owns 1,021 shares of BlackRock, Inc., and through a 401(k) account Mr. Wagner owns 3,665 shares of BlackRock, Inc.</footnote></footnotes><ownerSignature><signatureName>Salvatore Rappa</signatureName><signatureDate>2003-07-03</signatureDate></ownerSignature></ownershipDocument>

