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

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2007-01-31</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000865941</issuerCik>
        <issuerName>CELADON GROUP INC</issuerName>
        <issuerTradingSymbol>CLDN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001388496</rptOwnerCik>
            <rptOwnerName>Core Kenneth</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE CELADON DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2>9503 EAST 33RD STREET</rptOwnerStreet2>
            <rptOwnerCity>INDIANAPOLIS</rptOwnerCity>
            <rptOwnerState>IN</rptOwnerState>
            <rptOwnerZipCode>46235</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President and Secretary</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10800</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (Right-to-Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.22</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2010-06-26</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (Right-to-Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.67</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2010-11-30</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (Right-to-Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.71</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2011-09-07</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2250</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (Right-to-Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.71</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2011-10-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2250</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (Right-to-Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>12.81</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F5"/>
            </exerciseDate>
            <expirationDate>
                <value>2016-01-12</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>9450</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Original grant was an option to purchase 2,000 shares of the Issuer?s Common Stock, which vested 667, 667, and 666 on 06/26/2001, 06/26/2002, and 06/26/2003, respectively.  The derivative security reported in Table II has been adjusted for the 3-for-2 stock splits declared on 02/01/2006 and 06/01/2006.  Upon exercise, the derivative security converts on a one-to-one basis into the Issuer?s Common Stock.</footnote>
        <footnote id="F2">Original grant was an option to purchase 2,000 shares of the Issuer?s Common Stock, which vested 667, 667, and 666 on 11/30/2001, 11/30/2002, and 11/30/2003, respectively.  The derivative security reported in Table II has been adjusted for the 3-for-2 stock splits declared on 02/01/2006 and 06/01/2006.  Upon exercise, the derivative security converts on a one-to-one basis into the Issuer?s Common Stock.</footnote>
        <footnote id="F3">Original grant was an option to purchase 1,000 shares of the Issuer?s Common Stock, which vested 334, 333, and 333 on 09/07/2002, 09/07/2003, and 09/07/2004, respectively.  The derivative security reported in Table II has been adjusted for the 3-for-2 stock splits declared on 02/01/2006 and 06/01/2006. Upon exercise, the derivative security converts on a one-to-one basis into the Issuer?s Common Stock.</footnote>
        <footnote id="F4">Original grant was an option to purchase 1,000 shares of the Issuer?s Common Stock, which vested 334, 333, and 333 on 10/01/2002, 10/01/2003, and 10/01/2004.  The derivative security has been adjusted for the 3-for-2 stock splits declared on 02/01/2006 and 06/01/2006.  Upon exercise, the derivative security converts on a one-to-one basis into the Issuer?s Common Stock.</footnote>
        <footnote id="F5">Original grant was an option to purchase 4,200 shares of the Issuer's Common Stock, which vested 1,050 on 01/12/2007 and becomes exercisable with respect to the remaining shares as they vest 1,050, 1,050, and 1,050 on 01/12/2008, 01/12/2009, and 01/12/2010.  The derivative security has been adjusted for the 3-for-2 stock split declared on 02/01/2006 and 06/01/2006.  Upon exercise, the derivative security converts on a one-to-one basis into the Issuer?s Common Stock.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Kenneth Core, by Heidi Hornung-Scherr, attorney-in-fact, pursuant to a Power of Attorney filed herewith</signatureName>
        <signatureDate>2007-02-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
