<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
<periodOfReport>2003-11-14</periodOfReport>
<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000916085</issuerCik>
        <issuerName>HEALTH NET INC</issuerName>
        <issuerTradingSymbol>HNT</issuerTradingSymbol>
</issuer>
<reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001213947</rptOwnerCik>
            <rptOwnerName>WOYS JAMES</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>21650 OXNARD STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WOODLAND HILLS</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>91367</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector>
<isOfficer>1</isOfficer>
<isTenPercentOwner>0</isTenPercentOwner>
<isOther>0</isOther>
<officerTitle>President Health Net Fed Srvcs</officerTitle>
<otherText></otherText>
</reportingOwnerRelationship>
</reportingOwner>
<nonDerivativeTable><nonDerivativeTransaction><securityTitle><value>Class A Common Stock</value>
</securityTitle>
<transactionDate><value>2003-11-14</value>
</transactionDate>
<transactionCoding><transactionFormType>4</transactionFormType>
<transactionCode>M</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
<footnoteId id="F1"></footnoteId>
</transactionCoding>
<transactionAmounts><transactionShares><value>2480</value>
</transactionShares>
<transactionPricePerShare><value>12.9375</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode><value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<postTransactionAmounts><sharesOwnedFollowingTransaction><value>11218</value>
<footnoteId id="F3"></footnoteId>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>D</value>
</directOrIndirectOwnership>
</ownershipNature>
</nonDerivativeTransaction>
<nonDerivativeTransaction><securityTitle><value>Class A Common Stock</value>
</securityTitle>
<transactionDate><value>2003-11-14</value>
</transactionDate>
<transactionCoding><transactionFormType>4</transactionFormType>
<transactionCode>S</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionAmounts><transactionShares><value>1900</value>
</transactionShares>
<transactionPricePerShare><value>32.75</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode><value>D</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<postTransactionAmounts><sharesOwnedFollowingTransaction><value>9318</value>
<footnoteId id="F3"></footnoteId>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>D</value>
</directOrIndirectOwnership>
</ownershipNature>
</nonDerivativeTransaction>
<nonDerivativeTransaction><securityTitle><value>Class A Common Stock</value>
</securityTitle>
<transactionDate><value>2003-11-14</value>
</transactionDate>
<transactionCoding><transactionFormType>4</transactionFormType>
<transactionCode>S</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionAmounts><transactionShares><value>580</value>
</transactionShares>
<transactionPricePerShare><value>32.76</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode><value>D</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<postTransactionAmounts><sharesOwnedFollowingTransaction><value>8738</value>
<footnoteId id="F3"></footnoteId>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>D</value>
</directOrIndirectOwnership>
</ownershipNature>
</nonDerivativeTransaction>
</nonDerivativeTable>
<derivativeTable><derivativeTransaction><securityTitle><value>Option (Right to Buy)</value>
</securityTitle>
<conversionOrExercisePrice><value>12.9375</value>
</conversionOrExercisePrice>
<transactionDate><value>2003-11-14</value>
</transactionDate>
<transactionCoding><transactionFormType>4</transactionFormType>
<transactionCode>M</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
<footnoteId id="F1"></footnoteId>
</transactionCoding>
<transactionAmounts><transactionShares><value>2480</value>
</transactionShares>
<transactionPricePerShare><value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode><value>D</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<exerciseDate><value>2002-04-10</value>
</exerciseDate>
<expirationDate><value>2003-12-04</value>
</expirationDate>
<underlyingSecurity><underlyingSecurityTitle><value>Class A Common Stock</value>
</underlyingSecurityTitle>
<underlyingSecurityShares><value>2480</value>
</underlyingSecurityShares>
</underlyingSecurity>
<postTransactionAmounts><sharesOwnedFollowingTransaction><value>35900</value>
<footnoteId id="F2"></footnoteId>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>D</value>
</directOrIndirectOwnership>
</ownershipNature>
</derivativeTransaction>
</derivativeTable>
<footnotes><footnote id="F1">Exercise of an Option (Right to Buy) granted to the Reporting Person on December 4, 1998 under the Issuer's 1997 Stock Option Plan in a transaction exempt under Rule 16b-3 of the Securities Exchange Act of 1934, as amended.</footnote>
<footnote id="F2">Represents unexercised options from the December 4, 1998 option grant to the Reporting Person beneficially owned by the Reporting Person.</footnote>
<footnote id="F3">Includes 5,450 shares in which the Reporting Person has a beneficial ownership interest in under the Issuer's tax qualified Section 401(k) Savings Plan.</footnote>
</footnotes>
<ownerSignature><signatureName>/s/ James E. Woys, President Health Net Federal Services</signatureName>
<signatureDate>2003-11-18</signatureDate>
</ownerSignature>
</ownershipDocument>

