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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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<SEC-DOCUMENT>0001287256-04-000001.txt : 20041201
<SEC-HEADER>0001287256-04-000001.hdr.sgml : 20041201
<ACCEPTANCE-DATETIME>20041201140114
ACCESSION NUMBER:		0001287256-04-000001
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20041111
FILED AS OF DATE:		20041201
DATE AS OF CHANGE:		20041201

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BLUMENTHAL ARNOLD
		CENTRAL INDEX KEY:			0001287256

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-10004
		FILM NUMBER:		041176811

	MAIL ADDRESS:	
		STREET 1:		333 BAYVIEW AVENUE
		CITY:			AMITYVILLE
		STATE:			NY
		ZIP:			11701

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NAPCO SECURITY SYSTEMS INC
		CENTRAL INDEX KEY:			0000069633
		STANDARD INDUSTRIAL CLASSIFICATION:	COMMUNICATIONS EQUIPMENT, NEC [3669]
		IRS NUMBER:				112277818
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0630

	BUSINESS ADDRESS:	
		STREET 1:		333 BAYVIEW AVE
		CITY:			AMITYVILLE
		STATE:			NY
		ZIP:			11701
		BUSINESS PHONE:		5168429400

	MAIL ADDRESS:	
		STREET 1:		333 BAYVIEW AVE
		STREET 2:		XXXXXXXXXXXXXXXXXXX
		CITY:			AMITYVILLE
		STATE:			NY
		ZIP:			11701
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-11-11</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000069633</issuerCik>
        <issuerName>NAPCO SECURITY SYSTEMS INC</issuerName>
        <issuerTradingSymbol>NSSC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001287256</rptOwnerCik>
            <rptOwnerName>BLUMENTHAL ARNOLD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>333 BAYVIEW AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>AMITYVILLE</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>11701</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>NAPCO Security Systems, Inc</value>
            </securityTitle>
            <transactionDate>
                <value>2004-11-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>11.87</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1200</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Amount of Securities Beneficially Owned include the effect of the 20% Stock Dividend that was declared on November 8, 2004 with a record date of November 22,2004.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Arnold Blumenthal</signatureName>
        <signatureDate>2004-12-01</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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