<?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>0001059246</rptOwnerCik>
            <rptOwnerName>KAPITO ROBERT</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>Vice Chairman</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>18532</value></transactionShares><transactionPricePerShare><footnoteId id="F1"/></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>25850</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 beginnning on December 15, 2004.</footnote><footnote id="F2">Includes 500 shares of Class A Common Stock acquired by the reporting person under the BlackRock, Inc. Employee Stock Purchase Plan (the &quot;ESPP&quot;) on January 31, 2002 , 453 shares of Class A Common Stock acquired under the ESPP on July 31, 2002, 500 shares of Class A Common Stock acquired under the ESPP on January 31, 2003, and 76 shares of Class A Common Stock acquired under the ESPP on July 31, 2003. Also includes 789 shares of Class A Common Stock acquired through November 30, 2003 under the PNC Financial Services Group, Inc. Incentive Savings Plan (the &quot;ISP&quot;). The information on this report with respect to the ISP is based on a plan statement dated as of November 30, 2003.</footnote></footnotes><remarks/><ownerSignature><signatureName>Salvatore Rappa</signatureName><signatureDate>2003-12-19</signatureDate></ownerSignature></ownershipDocument>

