<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-12-18</periodOfReport>
    <issuer>
        <issuerCik>0001060021</issuerCik>
        <issuerName>BLACKROCK INC /NY</issuerName>
        <issuerTradingSymbol>BLK</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001210401</rptOwnerCik>
            <rptOwnerName>AUDET PAUL</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BLACKROCK FINANCIAL MANAGEMENT, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>40 EAST 52ND STREET</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Chief Financial Officer</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeTransaction><securityTitle><value>Shares of Class A Common Stock (par value $0.01 per share)</value><footnoteId id="F1"/></securityTitle><transactionDate><value>2003-12-18</value></transactionDate><deemedExecutionDate><value>2003-12-15</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>3042</value></transactionShares><transactionPricePerShare><footnoteId id="F1"/></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>8793</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeTransaction></nonDerivativeTable><footnotes><footnote id="F1">Restricted Stock granted pursuant to an award made under the BlackRock 1999 Stock Award and Incentive Plan, as amended. The shares become unrestricted in four equal annual installments beginning on December 15, 2004.</footnote><footnote id="F2">Includes 393 shares of Class A Common Stock acquired under the BlackRock, Inc. Employee Stock Purchase Plan (the &quot;ESPP&quot;) on January 31, 2003 and 362 shares of Class A Common Stock acquired under the ESPP on July 31, 2003</footnote></footnotes><remarks/><ownerSignature><signatureName>Salvatore Rappa</signatureName><signatureDate>2003-12-19</signatureDate></ownerSignature></ownershipDocument>

