EXHIBIT 99.3

Please Vote, Sign, Date and Return Promptly in the Enclosed Envelope.

Extraordinary General Meeting of Shareholders Proxy Card - CDT Environmental Technology Investment Holdings Limited

DETACH PROXY CARD HERE TO VOTE BY MAIL

THE BOARD OF DIRECTORS RECOMMENDS A VOTE “FOR” ALL LISTED PROPOSALS

PROPOSAL 1 – SHARE CAPITAL CHANGES PROPOSAL

RESOLVED, as an ordinary resolution that, the Company amend its authorised share capital with immediate effect in the manner and order set out below (collectively, the Share Capital Changes):

(a)    18,800,000 of the authorised ordinary shares of par value US$0.0025 each (including all of the existing issued ordinary shares) in the Company will be re-designated and reclassified as 18,800,000 class A ordinary shares of par value US$0.0025 each, where the rights of the existing ordinary shares shall be the same as such class A ordinary shares;

(b)    1,200,000 authorised but unissued ordinary shares of par value of US$0.0025 each in the Company will be cancelled and a new class of shares comprising of 1,200,000 class B ordinary shares of par value US$0.0025 each, which will be entitled to twenty (20) votes per share, with the rights and privileges as set out in the Amended MAA (as defined below) will be created; and

(c)    the authorised share capital of the Company be increased from US$50,000 to US$250,000 by the creation of 75,200,000 class A ordinary shares of par value US$0.0025 each and 4,800,000 class B ordinary shares of par value US$0.0025 each, such that the authorised share capital of the Company shall become US$250,000 divided into (i) 94,000,000 class A ordinary shares of par value US$0.0025 each and (ii) 6,000,000 class B ordinary shares of par value US$0.0025 each.

PROPOSAL 2 – CHARTER AMENDMENT PROPOSAL

RESOLVED, as a special resolution that, the proposed second amended and restated memorandum and articles of association of the Company, the form of which is attached to the notice of extraordinary general meeting as Appendix 1 (the Amended MAA), be adopted in its entirety and in substitution for and to the exclusion of the existing memorandum and articles of association of the Company with effect immediately after Share Capital Changes taking effect.

NOTE: To transact such other business as may be properly brought before the Extraordinary General Meeting and any adjournments thereof.

Note: This proxy must be signed exactly as the name appears hereon. When shares are held jointly, each holder should sign. When signing as executor, administrator, attorney, trustee or guardian, please give full title as such. If the signer is a corporation, please sign full corporate name by a duly authorized officer, giving full title as such. If signer is a partnership, please sign in partnership name by an authorized person.

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CDT Environmental Technology Investment Holdings Limited
Extraordinary General Meeting of Shareholders

September 23, 2025

at 9:30 a.m. (Local Time)

Proxy Material for this Meeting is available online at:
https://ts.vstocktransfer.com/irhlogin/I-CDTG

DETACH PROXY CARD HERE TO VOTE BY MAIL

THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS

The undersigned, being a registered holder of shares in CDT Environmental Technology Investment Holdings Limited (the “Company”), hereby appoints the Chairman of the Extraordinary General Meeting as proxy to attend and act on behalf of the undersigned at the Extraordinary General Meeting of the Company and at any adjournment(s) or postponement(s) thereof. Each share is entitled to one vote.

The proxy is authorized to vote on the resolutions set out in the notice convening the meeting as indicated above, or if no indication is given, to vote as the proxy thinks fit. The proxy is also entitled to vote at their discretion on any other resolution properly put to the meeting.

IMPORTANT: IF YOU WISH TO VOTE FOR THE RESOLUTIONS, TICK THE APPROPRIATE BOX MARKED   “FOR”. IF YOU WISH TO VOTE AGAINST THE RESOLUTIONS, TICK THE APPROPRIATE BOX MARKED “AGAINST”. IF YOU WISH TO ABSTAIN FROM VOTING ON A PARTICULAR RESOLUTION, TICK THE APPROPRIATE BOX MARKED “ABSTAIN”.

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PLEASE INDICATE YOUR VOTE ON THE REVERSE SIDE

(Continued and to be signed on Reverse Side)