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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-12-16</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001477415</rptOwnerCik>
            <rptOwnerName>Kimbro Ken</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2200 DON TYSON PARKWAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SPRINGDALE</rptOwnerCity>
            <rptOwnerState>AR</rptOwnerState>
            <rptOwnerZipCode>72762</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP &amp; Chief HR Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2013-12-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>24474</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>2014-02-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F3"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>387</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2406</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>2014-02-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>20025</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>38.42</value>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4449</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></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 4,449 shares of Class A Common Stock which vest on the fourth business day following the filing the Issuer's Annual Report on Form 10-K for its 2016 fiscal year if the performance metrics described in the applicable Stock Incentive Agreement (the Incentive Agreement) are achieved. The performance metrics are achievement of a three year (fiscal 2014-2016) cumulative EBIT target as set forth in the Incentive Agreement. If the performance metrics are not achieved, the award expires.</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 reporting requirements pursuant to Rule 16b-3.</footnote>
        <footnote id="F4">This is a weighted average price. These shares were sold in multiple transactions on February 18, 2014 at prices ranging from $38.40 to $38.47, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within this range.</footnote>
        <footnote id="F5">Represents 4,449 shares of Class A Common Stock which vest on the fourth business day following the filing the Issuer's Annual Report on Form 10-K for its 2016 fiscal year if the performance metrics described in the applicable Stock Incentive Agreement (the Incentive Agreement) are achieved. The performance metrics are achievement of a three year (fiscal 2014-2016) cumulative EBIT target as set forth in the Incentive Agreement. If the performance metrics are not achieved, the award expires.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Ken Kimbro</signatureName>
        <signatureDate>2014-02-19</signatureDate>
    </ownerSignature>
</ownershipDocument>
[{"type": "4", "sequence": "1", "filename": "wf-form4_139284581918881.xml", "description": "FORM 4", "secsgml_size_bytes": 8346}]
X0306
4
2013-12-16
0
0000100493
TYSON FOODS INC
TSN
0001477415
Kimbro Ken
2200 DON TYSON PARKWAY
SPRINGDALE
AR
72762
0
1
0
0
EVP & Chief HR Officer
Class A Common Stock
2013-12-16
4
J
0
10
0
A
24474
D
Class A Common Stock
2014-02-13
4
J
0
387
0
A
2406
I
Employee Stock Purchase Plan
Class A Common Stock
2014-02-18
4
S
0
20025
38.42
D
4449
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 4,449 shares of Class A Common Stock which vest on the fourth business day following the filing the Issuer's Annual Report on Form 10-K for its 2016 fiscal year if the performance metrics described in the applicable Stock Incentive Agreement (the Incentive Agreement) are achieved. The performance metrics are achievement of a three year (fiscal 2014-2016) cumulative EBIT target as set forth in the Incentive Agreement. If the performance metrics are not achieved, the award expires.
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 reporting requirements pursuant to Rule 16b-3.
This is a weighted average price. These shares were sold in multiple transactions on February 18, 2014 at prices ranging from $38.40 to $38.47, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within this range.
Represents 4,449 shares of Class A Common Stock which vest on the fourth business day following the filing the Issuer's Annual Report on Form 10-K for its 2016 fiscal year if the performance metrics described in the applicable Stock Incentive Agreement (the Incentive Agreement) are achieved. The performance metrics are achievement of a three year (fiscal 2014-2016) cumulative EBIT target as set forth in the Incentive Agreement. If the performance metrics are not achieved, the award expires.
Ken Kimbro
2014-02-19