<?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>0001059245</rptOwnerCik>
            <rptOwnerName>FINK LAURENCE</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>1</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Chairman and CEO</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>46841</value></transactionShares><transactionPricePerShare><footnoteId id="F1"/></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>54325</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 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, 2003 and 174 shares of Class A Common Stock acquired under the ESPP on July 31, 2003. Also includes 810 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 in 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>

