<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-09-15</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000100493</issuerCik>
        <issuerName>TYSON FOODS INC</issuerName>
        <issuerTradingSymbol>TSN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001554533</rptOwnerCik>
            <rptOwnerName>Grimes Sally</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>400 S. JEFFERSON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60607</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Pres and Global Growth Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-09-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>125.6883</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>54460.6883</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-11-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F3"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>661.0357</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1846.0357</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Employee Stock Purchase Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-11-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F4"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>8432.475</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>62893.1633</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Performance Shares</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2015-11-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F5"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>33729.90</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F5"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F5"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F5"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>33729.9</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>33729.90</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Non-Qualified Stock Options (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>50.0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2015-11-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F6"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>36759</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>50</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2016-11-30</value>
            </exerciseDate>
            <expirationDate>
                <value>2025-11-30</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>36759.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>36759</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents shares of the Issuer's Class A Common Stock received by the Reporting Person pursuant to the Issuer's dividend reinvestment plan since the last Statement of Changes in Beneficial Ownership was filed by the Reporting Person. Such acquisitions are exempt from Section 16 reporting requirements pursuant to Rule 16a-11.</footnote>
        <footnote id="F2">Includes 7,766.0196 shares of Class A Common Stock which vest on the fourth business day following the filing of the Issuer's Annual Report on Form 10-K for its 2017 fiscal year if the performance criterion described in the applicable Stock Incentive Agreement is achieved; and 46,694.6687 shares of Class A Common Stock which vest on July 1, 2018 if the performance criterion described in the applicable Stock Incentive Agreement is achieved.</footnote>
        <footnote id="F3">Represents shares of the Issuer's Class A Common Stock purchased for the Reporting Person's account under the Issuer's Employee Stock Purchase Plan since the last Statement of Changes in Beneficial Ownership was filed by the Reporting Person.  Such acquisitions are exempt from Section 16 concurrent reporting requirements pursuant to Rule 16b-3.</footnote>
        <footnote id="F4">Award of Class A Common Stock which vests on the fourth business day following the filing of the Issuer's Annual Report on Form 10-K for its 2018 fiscal year if the performance criterion described in the applicable Stock Incentive Agreement is achieved. The performance criterion is achievement of a three year (fiscal 2016-2018) cumulative EBIT target as set forth in the Stock Incentive Agreement. If the performance criterion is not achieved, the award expires.</footnote>
        <footnote id="F5">Award of performance Class A Common Stock which vests on the fourth business day following the filing of the Issuer's Annual Report on Form 10-K for its 2018 fiscal year if the performance metrics described in the applicable Stock Incentive Agreement are achieved. The performance criteria set forth in the Stock Incentive Agreement are (1) achievement of a three year (fiscal 2016-2018) cumulative EBIT target and (2) a favorable comparison of the market price of the Issuer's Class A Common Stock to a predetermined peer group of publicly traded companies over a three year (fiscal 2016-2018) period. Subject to the achievement of the performance criteria, the performance shares could vest at a level of 50%-200% and are reported as derivative securities at the 200% level. If neither of the performance criteria is achieved, the award expires.</footnote>
        <footnote id="F6">The stock options vest at 33 1/3% on each of the first, second, and third anniversary dates of the grant.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ R. Read Hudson by Power of Attorney for Sally Grimes</signatureName>
        <signatureDate>2015-12-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
[{"type": "4", "sequence": "1", "filename": "wf-form4_144908491320748.xml", "description": "FORM 4", "secsgml_size_bytes": 13064}]
X0306
4
2015-09-15
0
0000100493
TYSON FOODS INC
TSN
0001554533
Grimes Sally
400 S. JEFFERSON STREET
CHICAGO
IL
60607
0
1
0
0
Pres and Global Growth Officer
Class A Common Stock
2015-09-15
4
J
0
125.6883
0
A
54460.6883
D
Class A Common Stock
2015-11-19
4
J
0
661.0357
0
A
1846.0357
I
Employee Stock Purchase Plan
Class A Common Stock
2015-11-30
4
A
0
8432.475
0
A
62893.1633
D
Performance Shares
2015-11-30
4
A
0
33729.90
A
Class A Common Stock
33729.9
33729.90
D
Non-Qualified Stock Options (Right to Buy)
50.0
2015-11-30
4
A
0
36759
50
A
2016-11-30
2025-11-30
Class A Common Stock
36759.0
36759
D
Represents shares of the Issuer's Class A Common Stock received by the Reporting Person pursuant to the Issuer's dividend reinvestment plan since the last Statement of Changes in Beneficial Ownership was filed by the Reporting Person. Such acquisitions are exempt from Section 16 reporting requirements pursuant to Rule 16a-11.
Includes 7,766.0196 shares of Class A Common Stock which vest on the fourth business day following the filing of the Issuer's Annual Report on Form 10-K for its 2017 fiscal year if the performance criterion described in the applicable Stock Incentive Agreement is achieved; and 46,694.6687 shares of Class A Common Stock which vest on July 1, 2018 if the performance criterion described in the applicable Stock Incentive Agreement is achieved.
Represents shares of the Issuer's Class A Common Stock purchased for the Reporting Person's account under the Issuer's Employee Stock Purchase Plan since the last Statement of Changes in Beneficial Ownership was filed by the Reporting Person.  Such acquisitions are exempt from Section 16 concurrent reporting requirements pursuant to Rule 16b-3.
Award of Class A Common Stock which vests on the fourth business day following the filing of the Issuer's Annual Report on Form 10-K for its 2018 fiscal year if the performance criterion described in the applicable Stock Incentive Agreement is achieved. The performance criterion is achievement of a three year (fiscal 2016-2018) cumulative EBIT target as set forth in the Stock Incentive Agreement. If the performance criterion is not achieved, the award expires.
Award of performance Class A Common Stock which vests on the fourth business day following the filing of the Issuer's Annual Report on Form 10-K for its 2018 fiscal year if the performance metrics described in the applicable Stock Incentive Agreement are achieved. The performance criteria set forth in the Stock Incentive Agreement are (1) achievement of a three year (fiscal 2016-2018) cumulative EBIT target and (2) a favorable comparison of the market price of the Issuer's Class A Common Stock to a predetermined peer group of publicly traded companies over a three year (fiscal 2016-2018) period. Subject to the achievement of the performance criteria, the performance shares could vest at a level of 50%-200% and are reported as derivative securities at the 200% level. If neither of the performance criteria is achieved, the award expires.
The stock options vest at 33 1/3% on each of the first, second, and third anniversary dates of the grant.
/s/ R. Read Hudson by Power of Attorney for Sally Grimes
2015-12-02