<SEC-DOCUMENT>0000911177-25-000039.txt : 20250303
<SEC-HEADER>0000911177-25-000039.hdr.sgml : 20250303
<ACCEPTANCE-DATETIME>20250303162801
ACCESSION NUMBER:		0000911177-25-000039
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250227
FILED AS OF DATE:		20250303
DATE AS OF CHANGE:		20250303

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CASELLA JOHN W
		CENTRAL INDEX KEY:			0001055352
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-23211
		FILM NUMBER:		25698414

	MAIL ADDRESS:	
		STREET 1:		CASELLA WASTE SYSTEMS INC
		STREET 2:		25 GREENS HILL LN
		CITY:			RUTLAND
		STATE:			VT
		ZIP:			05701

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CASELLA WASTE SYSTEMS INC
		CENTRAL INDEX KEY:			0000911177
		STANDARD INDUSTRIAL CLASSIFICATION:	REFUSE SYSTEMS [4953]
		ORGANIZATION NAME:           	01 Energy & Transportation
		IRS NUMBER:				030338873
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		25 GREENS HILL ROAD
		CITY:			RUTLAND
		STATE:			VT
		ZIP:			05701
		BUSINESS PHONE:		8027750325

	MAIL ADDRESS:	
		STREET 1:		25 GREENS HILL ROAD
		CITY:			RUTLAND
		STATE:			VT
		ZIP:			05701
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wk-form4_1741037274.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-02-27</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000911177</issuerCik>
        <issuerName>CASELLA WASTE SYSTEMS INC</issuerName>
        <issuerTradingSymbol>CWST</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001055352</rptOwnerCik>
            <rptOwnerName>CASELLA JOHN W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CASELLA WASTE SYSTEMS</rptOwnerStreet1>
            <rptOwnerStreet2>25 GREENS HILL LANE</rptOwnerStreet2>
            <rptOwnerCity>RUTLAND</rptOwnerCity>
            <rptOwnerState>VT</rptOwnerState>
            <rptOwnerZipCode>05701</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CHIEF EXECUTIVE OFFICER</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-02-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>29106</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>39835</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-03-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>13577</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>113.88</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>26258</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>694</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Spouse</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class B Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>166000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class B Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>137000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>by SLAT 2</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class B Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>134000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By SLAT</value>
                    <footnoteId id="F6"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class B Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>57100</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Spouse</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents shares of Class A Common Stock acquired by the reporting person upon the vesting of performance-based stock units (PSUs) granted to the reporting person on March 11, 2022, as a result of the level of achievement by the issuer of certain performance objectives during the period running from January 1, 2024 through December 31, 2024, and a multiplier based on relative total shareholder return for the period running from January 1, 2022 to December 31, 2024, as certified by the issuer's compensation and human capital committee on February 27, 2025.</footnote>
        <footnote id="F2">Represents the sale of shares of Class A Common Stock pursuant to a &quot;sell-to-cover&quot; transaction in order to satisfy tax withholding obligations in connection with the vesting of PSUs previously granted to the reporting person on March 11, 2022. This sale was effected pursuant to an automatic sell-to-cover instruction adopted by the reporting person on May 12, 2022 and does not represent a discretionary sale by the reporting person.</footnote>
        <footnote id="F3">Represents the weighted average sales price for shares sold in multiple transactions, ranging from $113.38 to $114.27. Upon request of the staff of the Securities and Exchange Commission, the issuer or a security holder of the issuer, the reporting person will provide full information regarding the number of shares sold at each separate price.</footnote>
        <footnote id="F4">Held by Mr. Casella's spouse.  Mr. Casella disclaims beneficial ownership of the securities indicated to the extent to which he does not have an actual pecuniary interest in such securities.</footnote>
        <footnote id="F5">Held by the Spousal Lifetime Access Trust for the benefit of Mr. Casella (&quot;SLAT 2&quot;). Mr. Casella is the trustee of the SLAT 2.</footnote>
        <footnote id="F6">Held by the Spousal Lifetime Access Trust for the benefit of Mr. Casella's spouse (&quot;SLAT&quot;). Mr. Casella's spouse is the trustee of the SLAT. Mr. Casella disclaims beneficial ownership of the securities indicated to the extent to which he does not have an actual pecuniary interest in such securities.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ John W. Casella</signatureName>
        <signatureDate>2025-03-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
