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

    <schemaVersion>X0609</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-06-01</periodOfReport>

    <notSubjectToSection16>true</notSubjectToSection16>

    <issuer>
        <issuerCik>0001489096</issuerCik>
        <issuerName>Thermon Group Holdings, Inc.</issuerName>
        <issuerTradingSymbol>THR</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001912901</rptOwnerCik>
            <rptOwnerName>Roberto Kuahara</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>7171 SOUTHWEST PARKWAY</rptOwnerStreet1>
            <rptOwnerStreet2>BUILDING 300, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>AUSTIN</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>78735</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>true</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle>SVP, Operations</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-06-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>16269</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>59807</value>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-06-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>59807</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Pursuant to the terms of the Agreement and Plan of Merger dated February 23, 2026 (the &quot;Merger Agreement&quot;) by and among the Issuer, CECO Environmental Corp (&quot;CECO&quot;), and two wholly-owned merger subsidiaries of CECO (the &quot;Merger Subs&quot;), the Issuer merged with the two Merger Subs to become a wholly-owned subsidiary of CECO (the &quot;Merger&quot;).</footnote>
        <footnote id="F2">Represents shares underlying Issuer performance unit awards (&quot;PU awards&quot;) that vested in accordance with the terms of the Merger Agreement immediately prior to the effective time of the Merger.</footnote>
        <footnote id="F3">The number of shares of Issuer common stock deemed subject to each Issuer PU award was determined as follows: (a) for any completed performance period, based on actual achievement of the applicable performance-based vesting conditions; (b) for any performance period in which the effective time of the Merger occurred (i.e., the performance period was not yet completed and performance goals had been established), based on the greater of target performance and actual performance as of the effective time of the Merger (with performance goals and achievement thereof equitably adjusted as necessary to reflect a shortened performance period); and (c) for any performance period for which performance goals had not yet been established, based on target performance.</footnote>
        <footnote id="F4">Pursuant to the terms of the Merger Agreement, each share of Issuer common stock (other than excluded and dissenting shares) was converted into the right to receive, at the election of the holder, one of the following forms of merger consideration, subject to proration as described in the Merger Agreement: (i) 0.6840 shares of CECO common stock and $10.00 in cash, without interest (the &quot;mixed consideration&quot;), which is the default election; (ii) $63.89 in cash, without interest (the &quot;cash consideration&quot;); or (iii) 0.8110 shares of CECO common stock (the &quot;stock consideration&quot;). The reporting person elected the mixed consideration for their shares of Issuer common stock.</footnote>
        <footnote id="F5">Includes 12,041 shares of Issuer common stock underlying Issuer restricted stock unit awards (&quot;RSU awards&quot;) held by the reporting person. Pursuant to the terms of the Merger Agreement, each outstanding Issuer RSU award was automatically assumed by CECO and converted into a CECO RSU award with respect to a number of shares of CECO common stock (rounded down to the nearest whole share) equal to the product of (a) the number of shares of Issuer common stock subject to such Issuer RSU award immediately prior to the effective time of the Merger and (b) 0.8110. Each such converted CECO RSU award is otherwise subject to the same terms and conditions (including vesting or forfeiture) as applied to the corresponding Issuer RSU award immediately prior to the effective time of the Merger, except as otherwise required by applicable law.</footnote>
        <footnote id="F6">Includes 16,269 shares of Issuer common stock underlying Issuer PU awards held by the reporting person. Pursuant to the terms of the Merger Agreement, each outstanding Issuer PU award was automatically assumed by CECO and converted into a CECO RSU award with respect to a number of shares of CECO common stock (rounded down to the nearest whole share) equal to the product of (a) the number of shares of Issuer common stock subject to such Issuer PU award immediately prior to the effective time of the Merger (determined in accordance with the formula set forth in footnote 3) and (b) 0.8110. Each such converted CECO RSU award is subject to the same terms and conditions (including any time-based vesting and forfeiture provisions and, as applicable, dividend equivalent rights) as applied to the corresponding Issuer PU award immediately prior to the effective time of the Merger, except as otherwise required by applicable law, but is no longer subject to performance-based vesting conditions.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Ryan Tarkington, Attorney-in-Fact</signatureName>
        <signatureDate>2026-06-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
