-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 ATTrsDLVmJZmU1YdVLDmuiWZAiZNJyWku2YQxZE0y01YrgFMeCWM48lQyrB19g3u
 eICQO05q8OyfmBa11u4mAQ==

<SEC-DOCUMENT>0001140361-11-005779.txt : 20110202
<SEC-HEADER>0001140361-11-005779.hdr.sgml : 20110202
<ACCEPTANCE-DATETIME>20110202201248
ACCESSION NUMBER:		0001140361-11-005779
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20110111
FILED AS OF DATE:		20110202
DATE AS OF CHANGE:		20110202

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			RAZDAN ASH
		CENTRAL INDEX KEY:			0001348803

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-25426
		FILM NUMBER:		11568185

	MAIL ADDRESS:	
		STREET 1:		11500 MOPAC EXPWY. BLDG C
		CITY:			AUSTIN
		STATE:			TX
		ZIP:			78759

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NATIONAL INSTRUMENTS CORP /DE/
		CENTRAL INDEX KEY:			0000935494
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-PREPACKAGED SOFTWARE [7372]
		IRS NUMBER:				741871327
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		11500 NORTH MOPAC EXPRESSWAY
		CITY:			AUSTIN
		STATE:			TX
		ZIP:			78759
		BUSINESS PHONE:		5123389119

	MAIL ADDRESS:	
		STREET 1:		11500 NORTH MOPAC EXPRESSWAY
		CITY:			AUSTIN
		STATE:			TX
		ZIP:			78759
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4/A
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2011-01-11</periodOfReport>

    <dateOfOriginalSubmission>2011-01-13</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000935494</issuerCik>
        <issuerName>NATIONAL INSTRUMENTS CORP /DE/</issuerName>
        <issuerTradingSymbol>NATI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001348803</rptOwnerCik>
            <rptOwnerName>RAZDAN ASH</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>11500 NORTH MOPAC, BLDG C</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>AUSTIN</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>78759</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <officerTitle></officerTitle>
            <otherText>Dir Corp Dev &amp; Ofc of Pres</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2011-01-11</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>39.45</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>50277</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Shares were sold under Reporting Person's 10(b)5-1 Plan.</footnote>
        <footnote id="F2">The securities beneficially owned were erroneously reported as 52,277. Each line of the securities beneficially owned on the Form 4 filed Janaury 28, 2011 should also be reduced by 2,000 shares.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>David G. Hugley as attorney-in-fact for Ash Razdan</signatureName>
        <signatureDate>2011-02-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----