Exhibit 4.1


SPECIMEN UNIT CERTIFICATE


NUMBER UNITS

U-


SEE REVERSE FOR CERTAIN DEFINITIONS


CUSIP 048453 203


 


ATLANTIC COASTAL ACQUISITION CORP.


 


UNITS CONSISTING OF ONE SHARE OF CLASS
A COMMON STOCK AND ONE-THIRD OF ONE

WARRANT TO PURCHASE ONE SHARE OF CLASS A COMMON STOCK


 


THIS CERTIFIES THAT is the owner of Units.


 


Each Unit (“Unit”)
consists of one (1) share of Class A common stock, par value $0.0001 per share (“Common Stock”), of Atlantic
Coastal Acquisition Corp., a Delaware corporation (the “Company”), and one-third (1/3) of one redeemable
warrant (each whole warrant, a “Warrant”). Each whole Warrant entitles the holder to purchase one (1)
share (subject to adjustment) of Common Stock for $11.50 per share (subject to adjustment). Each Warrant will become exercisable
on the later of (i) thirty (30) days after the Company’s completion of a merger, capital stock exchange, asset acquisition,
stock purchase, reorganization or other similar business combination with one or more businesses (each a “Business
Combination”), or (ii) twelve (12) months from the closing of the Company’s initial public offering, and will
expire unless exercised before 5:00 p.m., New York City Time, on the date that is five (5) years after the date on which the Company
completes its initial Business Combination, or earlier upon redemption or liquidation. The Common Stock and Warrants comprising
the Units represented by this certificate are not transferable separately prior to [___], 2021, unless BTIG, LLC elects to allow
earlier separate trading, subject to the Company’s filing of a Current Report on Form 8-K with the Securities and Exchange
Commission containing an audited balance sheet reflecting the Company’s receipt of the gross proceeds of the Company’s
initial public offering and issuing a press release announcing when separate trading will begin. No fractional warrants will be
issued upon separation of the Units and only whole Warrants will trade. The terms of the Warrants are governed by a Warrant Agreement,
dated as of [___], 2021, between the Company and Continental Stock Transfer & Trust Company, as Warrant Agent, and are subject
to the terms and provisions contained therein, all of which terms and provisions the holder of this certificate consents to by
acceptance hereof. Copies of the Warrant Agreement are on file at the office of the Warrant Agent at Continental Stock Transfer
 & Trust Company, 1 State Street, 30th Floor, New York, New York 10004, and are available to any Warrant holder on written request
and without cost.


 


This certificate is not valid unless countersigned
by the Transfer Agent and Registrar of the Company.


 


This certificate shall be governed by and
construed in accordance with the internal laws of the State of New York.


 


Witness the facsimile signature of the
duly authorized officers of the Company.


 


	 	 
	[Chief Executive Officer]	 


 






     


     


    

 


ATLANTIC COASTAL ACQUISITION CORP.


 


The Company will furnish without charge
to each unitholder who so requests, a statement of the powers, designations, preferences and relative, participating, optional
or other special rights of each class of stock or series thereof of the Company and the qualifications, limitations, or restrictions
of such preferences and/or rights.


 


The following abbreviations, when used
in the inscription on the face of this certificate, shall be construed as though they were written out in full according to applicable
laws or regulations:


 


	TEN COM	-	as tenants in common	UNIF GIFT MIN ACT	-	 	Custodian	 
	TEN ENT	-	as tenants by the entireties	 	(Cust)	
        (Minor)

         

	JT TEN	-	as joint tenants with right of survivorship and not as tenants in common	 	 	under Uniform Gifts to Minors Act (State)


 


Additional abbreviations may also be used
though not in the above list.


 


For value received, hereby sells, assigns
and transfers unto


 


PLEASE INSERT SOCIAL SECURITY OR OTHER

IDENTIFYING NUMBER OF ASSIGNEE


 


(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS,
INCLUDING ZIP CODE, OF ASSIGNEE)


 


Units represented by the within Certificate,
and does hereby irrevocably constitute and appoint


 


Attorney to transfer
the said Units on the books of the within named Company with full power of substitution in the premises.


 


Dated


 


	 	 
	 	Notice: The signature to this assignment must correspond with the name as written upon the face of the certificate in every particular, without alteration or enlargement or any change whatever.


 


	Signature(s) Guaranteed:	 


 






     


     


    

 


THE SIGNATURE(S) MUST BE GUARANTEED BY
AN ELIGIBLE GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED
SIGNATURE GUARANTEE MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15 (OR ANY SUCCESSOR RULE UNDER THE SECURITIES EXCHANGE ACT
OF 1934, AS AMENDED).


 


In each case, as more fully described in
the Company’s final prospectus dated [___], 2021, the holder(s) of this certificate shall be entitled to receive a pro-rata
portion of certain funds held in the trust account established in connection with the Company’s initial public offering only
in the event that (i) the Company redeems the shares of Class A common stock sold in its initial public offering and liquidates
because it does not consummate an initial business combination by [___], 2023, (ii) the Company redeems the shares of Class A common
stock sold in its initial public offering in connection with a stockholder vote to amend the Company’s second amended and
restated certificate of incorporation (a) to modify the substance or timing of the Company’s obligation to allow redemption
in connection with the Company’s initial business combination or to redeem 100% of the Class A common stock if it does not
consummate an initial business combination by [___], 2023, or (b) with respect to any other provisions relating to stockholders’
rights or pre-initial business combination activity, or (iii) if the holder(s) seek(s) to redeem for cash his, her or its respective
shares of Class A common stock in connection with a tender offer (or proxy solicitation, solely in the event the Company seeks
stockholder approval of the proposed initial business combination) setting forth the details of a proposed initial business combination.
In no other circumstances shall the holder(s) have any right or interest of any kind in or to the trust account.