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

    <documentType>4</documentType><periodOfReport>2003-07-18</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>2003-07-18</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>P</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>150</value></transactionShares><transactionValue><value>45.31</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>6380</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value><footnoteId id="F1"/></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Shares of Class A Common Stock (par value $0.01 per share)</value></securityTitle><transactionDate><value>2003-07-18</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>P</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>120</value></transactionShares><transactionValue><value>45.32</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>6500</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value><footnoteId id="F1"/></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeSecurity><footnotes><footnote id="F1">Lawrence M. Wagner and his wife jointly own 1,544 shares of BlackRock, Inc. Mr. Wagner additionally owns 4,956 shares of BlackRock, Inc. individually, as follows: through a Keogh account Mr. Wagner owns 1,271 shares of BlackRock, Inc., and through a 401(k) account Mr. Wagner owns 3,685 shares of BlackRock, Inc.</footnote></footnotes><ownerSignature><signatureName>Salvatore Rappa</signatureName><signatureDate>2003-07-18</signatureDate></ownerSignature></ownershipDocument>

