NB Bancorp, Inc.

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No. )

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

☐Preliminary Proxy Statement

☐Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☒Definitive Proxy Statement

☐Definitive Additional Materials

☐Soliciting Material Pursuant to § 240.14a-12

NB Bancorp, Inc.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

☒No fee required.

☐Fee paid previously with preliminary materials.

☐Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

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Notice of Annual Meeting
of Shareholders and
Proxy Statement

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COMPANY CULTURE

130+ years

For the last 130+ years, we’ve worked to help our communities grow and develop with best-in-class products and services that make it possible for anyone to dream, do, and build almost anything.

$1.8M

The Bank is an active partner in the community and surpassed $1.8 million in contributions for 2025. We provide funding to organizations that support health and human services, education, financial literacy and the arts, with a focus on organizations that address social justice, homelessness and food insecurity issues.

OUR CLIENTS

We are honored to be the trusted advisors of the individuals and businesses who are navigating paths to greater growth and success. With speed, personalized attention, and rock-solid financial stability on their side, our clients will make the difference as they move our communities confidently into the future.

Build something lasting.

Build something special.

Build something with us.

OUR COMMUNITY

Community support isn’t just something that we talk about; it’s something that we do day in and day out because building communities is at the heart of our 130+ year heritage. Needham Bank strives to give over $1.5 million back to the community as charitable contributions annually and proudly supports over 300 local non-profits. Our support goes far beyond just writing a check, we aim to form meaningful and lasting partnerships with the organizations we work with.

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March 27, 2026 Dear Fellow Stockholder: Two years ago, we completed our initial public offering, generating over $400 million from investors to provide the opportunity to grow the balance sheet and provide returns to our shareholders. Since that time, we have grown our balance sheet by $2.5 billion, which includes the acquisition of Provident Bancorp, Inc. (“Provident Acquisition”) during 2025. 2025 brought many opportunities to continue our strategic initiative, which was initially put into place back in 2018. Excluding the Provident Acquisition during 2025, gross loans grew by 9.8% and core deposits grew by 11.3%, both higher than most of our peers. Additionally, as we continue to effectively manage our capital levels, we completed two share repurchase programs during the year and initiated a quarterly dividend midway through the year. The Provident Acquisition provided us with an expanded physical presence with 7 branches in a market where we were already providing credit to customers. This allows us to grow and move with our customers, while helping us to advance in our technology and innovation. Our operating results for 2025 speak for themselves, with operating net income of $66.7 million, which excludes merger-related and other one-time non-operating expenses, resulting in operating diluted earnings per share of $1.76, and operating return on average assets and equity of 1.21% and 8.73%, respectively. On behalf of the Board of Directors, we urge you to sign, date and return the enclosed proxy card as soon as possible, even if you currently plan to attend the annual meeting. This will not prevent you from voting during the meeting, but will assure that your vote is counted if you are unable to vote during the meeting. Your vote is important, regardless of the number of shares that you own. Our Proxy Statement and the 2025 Annual Report are available at: https://nbbancorp.com/financials/.

Sincerely,

JOSEPH CAMPANELLIFRANCIS ORFANELLO

Chairman, President & Chief Executive OfficerLead Independent Director

NB Bancorp, Inc. | 2026 Proxy Statement 1

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TABLE OF CONTENTS

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS	3
PROXY SUMMARY	4
VOTING SECURITIES AND PRINCIPAL HOLDERS	5
Principal Holders	5
Quorum	6
Votes Required	6
Participants in the Needham Bank Employee Stock Ownership Plan and Needham Bank 401(k) Plan	7
Compensation Highlights	8
Board Skills	9
Governance Highlights	10
PROPOSAL I—ELECTION OF DIRECTORS	11
Directors	12
Executive Officers Who are Not Directors	19
Board Independence	20
Board Leadership Structure and Risk Oversight	21
References to our Website Address	23
Delinquent Section 16(a) Reports	23
Code of Ethics for Senior Officers	23
Attendance at Annual Meetings of Stockholders	23
Policies and Practices Related to the Grant of Certain Equity Awards	23
Anti-Hedging Policy	23
Recoupment/Clawback Policy	24

Communications with the Board of Directors	24
Insider Trading Arrangements and Policy	24
Meetings and Committees of the Board of Directors	24
Audit Committee Report	26
Nominating and Governance Committee Procedures	29
Transactions With Certain Related Persons	32
Executive Compensation	32
Directors’ Compensation	39
PROPOSAL II—RATIFICATION OF APPOINTMENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM	41
STOCKHOLDERS PROPOSALS AND NOMINATIONS	42
OTHER MATTERS	43
MISCELLANEOUS	43
IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS	44
E-DELIVERY	45

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS: THE PROXY STATEMENT, INCLUDING THE NOTICE OF THE ANNUAL MEETING OF STOCKHOLDERS, AND NB BANCORP, INC.’S ANNUAL REPORT FOR THE YEAR ENDED DECEMBER 31, 2025 ARE EACH AVAILABLE AT HTTPS://NBBANCORP.COM/FINANCIALS/.

2 NB Bancorp, Inc. | 2026 Proxy Statement

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NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

WHEN

WHERE

RECORD DATE

Wednesday, April 29, 2026
12:00 p.m., Eastern time

Wellesley Gateway

93 Worcester Street

Wellesley, MA 02481

March 6, 2026

Notice is hereby given that the 2026 Annual Meeting of Stockholders of NB Bancorp, Inc. will be held on Wednesday, April 29, 2026, at 12:00 p.m., Eastern time.

A Proxy Card and Proxy Statement for the annual meeting are enclosed.

PROPOSALS FOR YOUR VOTE		BOARD VOTING RECOMMENDATION		FOR FURTHER DETAILS
1.	Election of five directors		FOR each nominee	See Page 11
2.	Ratifying the Appointment of our Independent Registered Public Accounting Firm for 2026		FOR	See Page 41

Such other matters as may properly come before the annual meeting, or any adjournments thereof. The Board of Directors is not aware of any other business to come before the annual meeting.

Any action may be taken on the foregoing proposals at the annual meeting on the date specified above, or on the date or dates to which the annual meeting may be adjourned. Stockholders of record at the close of business on March 6, 2026 are the stockholders entitled to vote at the annual meeting, and any adjournments thereof.

 

INTERNET

 

MOBILE VOTING

 

MAIL

www.cstproxyvote.com

Use the Internet to vote your proxy. Have your proxy card available when you access the above website. Follow the prompts to vote your shares.

On your Smartphone/ Tablet, open the QR Reader and scan the QR code found on your proxy card. Once the voting site is displayed, enter your Control Number from the proxy card and vote your shares.

Mark, sign and date your proxy card and return it in the postage-paid envelope provided.

EACH STOCKHOLDER IS REQUESTED TO SIGN, DATE AND RETURN THE ENCLOSED PROXY CARD WITHOUT DELAY IN THE ENCLOSED POSTAGE-PAID ENVELOPE OR VOTE VIA THE INTERNET OR MOBILE VOTING, PER THE INSTRUCTIONS INCLUDED ON THE ENCLOSED PROXY CARD. ANY PROXY GIVEN BY THE STOCKHOLDER MAY BE REVOKED AT ANY TIME BEFORE IT IS VOTED. A PROXY MAY BE REVOKED BY FILING WITH THE CORPORATE SECRETARY OF NB BANCORP, INC., A WRITTEN REVOCATION OR A DULY EXECUTED PROXY CARD BEARING A LATER DATE. ANY STOCKHOLDER PRESENT AT THE ANNUAL MEETING MAY REVOKE HIS OR HER PROXY AND VOTE PERSONALLY ON EACH MATTER BROUGHT BEFORE THE ANNUAL MEETING. HOWEVER, IF YOU ARE A STOCKHOLDER WHOSE SHARES ARE NOT REGISTERED IN YOUR OWN NAME, YOU WILL NEED ADDITIONAL DOCUMENTATION FROM YOUR RECORD HOLDER IN ORDER TO VOTE AT THE ANNUAL MEETING.

IMPORTANT: THE PROMPT RETURN OF PROXIES WILL SAVE THE COMPANY THE EXPENSE OF FURTHER REQUESTS FOR PROXIES. A SELF-ADDRESSED ENVELOPE IS ENCLOSED FOR YOUR CONVENIENCE. NO POSTAGE IS REQUIRED IF MAILED WITHIN THE UNITED STATES. IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS: THE PROXY STATEMENT, INCLUDING THE NOTICE OF THE ANNUAL MEETING OF STOCKHOLDERS, AND NB BANCORP, INC.’S ANNUAL REPORT FOR THE YEAR ENDED DECEMBER 31, 2025 ARE EACH AVAILABLE AT HTTPS://NBBANCORP.COM/FINANCIALS/.	By Order of the Board of Directors



		Denise Dunn
		Corporate Secretary

		Needham, Massachusetts
		March 27, 2026

NB Bancorp, Inc. | 2026 Proxy Statement 3

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PROXY SUMMARY

Director Nominees

					COMMITTEES
NOMINEES FOR DIRECTOR		IND	AGE	DIRECTOR SINCE	A	ERM	C	NG
	Paul Ayoub Chair Nutter McClennen & Fish LLP	✓	70	2023				n
	Joseph Campanelli Chairman, President & CEO Needham Bank		69	2017
	William Darcey President & CEO Provider Insurance Group	✓	63	2017		n
	Joseph Reilly Retired President & CEO Provident Bancorp, Inc. and BankProv		69	2025		n
	Mark Whalen Retired CEO Needham Bank	✓	67	2007	n	n	n	n
DIRECTORS WITH TERMS ENDING IN 2027
	Angela Jackson Chief Executive Officer Future Forward Strategies	✓	50	2023	n			n
	Joseph Nolan Chairman, President & CEO Eversource	✓	63	2023			n
	Hope Pascucci President & Principal Rose Grove Capital Management, LLC	✓	58	2023	n	n
	Raza Shaikh Managing Director Launchpad Venture Group	✓	52	2023	n	n
DIRECTORS WITH TERMS ENDING IN 2028
	Susan Elliott Retired Executive Vice President Federal Home Loan Bank of Boston	✓	72	2020	n
	Christopher Lynch President Marshall Resources	✓	64	2010			n
	Kenneth Montgomery Retired First Vice President and Chief Operating Officer Federal Reserve Bank of Boston	✓	67	2024		n		n
	Francis Orfanello Operating Partner One Rock Capital Partners	✓	67	2007	n	n	n

■ Chair ■ Member IND Independent

Committees: A Audit ERM Enterprise Risk Management C Compensation NG Nominating and Governance

Gender	Independence	AGE	TENURE

4 NB Bancorp, Inc. | 2026 Proxy Statement

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Voting Securities And Principal Holders

Except as otherwise noted below, holders of record of NB Bancorp, Inc.’s shares of common stock, par value $0.01 per share, as of the close of business on March 6, 2026 are entitled to one vote for each share then held. As of March 6, 2026, there were 45,165,174 shares of common stock issued and outstanding.

NB Bancorp, Inc.’s Articles of Incorporation provide that, subject to certain exceptions, record owners of the Company’s common stock that is beneficially owned by a person who beneficially owns in excess of 10% of the Company’s outstanding shares are not entitled to any vote in respect of the shares held in excess of the 10% limit.

Principal Holders

Persons and groups who beneficially own in excess of 5% of the shares of common stock are required to file certain reports with the Securities and Exchange Commission regarding such ownership. The following table sets forth, as of March 6, 2026, the shares of common stock beneficially owned by our directors and executive officers, individually and as a group, and by each person who was known to us as the beneficial owner of more than 5% of the outstanding shares of common stock. The mailing address for each of our directors and executive officers is 1063 Great Plain Avenue, Needham, MA 02492.


	Shares of Common
	Stock Beneficially		Percent of Shares of
	Owned as of the		Common Stock
Persons Owning Greater than 5%	Record Date⁽¹⁾		Outstanding⁽²⁾
Needham Bank Employee Stock Ownership Plan	3,339,757		7.4	%
1063 Great Plain Avenue
Needham, Massachusetts 02492

BlackRock, Inc.	3,103,770		6.9	%
50 Hudson Yards
New York, NY 10001

Pertento Partners	2,343,776		5.2	%
111 Park Street
London W1K7JL
United Kingdom

The Vanguard Group	2,301,034		5.1	%
100 Vanguard Blvd.
Malvern, PA 19355

Directors
Paul Ayoub	97,512	⁽³⁾	*
Joseph Campanelli	497,435	⁽⁴⁾	1.1%
William Darcey	162,639	⁽⁵⁾	*
Susan Elliott	117,195	⁽⁶⁾	*
Angela Jackson	81,255	⁽⁷⁾	*
Christopher Lynch	156,922	⁽⁸⁾	*
Kenneth Montgomery	85,140	⁽⁹⁾	*
Joseph Nolan

SEC Form DEF 14A filed by NB Bancorp Inc.