NB Bancorp (NBBK) CEO adds 2,500 shares in open-market stock purchase

Rhea-AI Filing Summary

NB Bancorp, Inc.’s President & CEO and Chairman Joseph P. Campanelli reported an open-market purchase of 2,500 shares of common stock at $20.16 per share. This buy on March 19, 2026 brought his direct holdings to 396,661 shares.

He also reports indirect ownership of common stock, including 47,000 shares held by an IRA, 49,597 shares held by a 401(k), 3,677 shares held by an ESOP, and 3,000 shares held as trustee for a trust. The filing notes that his reported holdings include restricted stock scheduled to vest in tranches beginning on April 24, 2026 and February 25, 2027.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
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hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

CAMPANELLI JOSEPH P

(Last) (First) (Middle)

1063 GREAT PLAIN AVE

(Street)

NEEDHAM MASSACHUSETTS 02492

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
NB Bancorp, Inc. [ NBBK ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
X	Officer (give title below)	X	Other (specify below)
	President & CEO		Chairman of the Board

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
03/19/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	03/19/2026		P		2,500	A	$20.16	396,661(1)(2)	D
Common Stock								47,000	I	By IRA
Common Stock								49,597	I	By 401(k)
Common Stock								3,677	I	By ESOP
Common Stock								3,000	I	As trustee for trust

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Includes shares of restricted stock which vest at a rate of 20% per year commencing on April 24, 2026.

2. Includes shares of restricted stock which vest at a rate of 33 1/3% per year commencing on February 25, 2027.

	/s/ Steven T. Lanter, pursuant to Power of Attorney	03/19/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

FAQ

What insider transaction did NB Bancorp (NBBK) report for Joseph P. Campanelli?

NB Bancorp (NBBK) reported that CEO Joseph P. Campanelli bought 2,500 common shares. The open-market purchase on March 19, 2026 was at a price of $20.16 per share and increased his directly held stake to 396,661 shares.

At what price did the NB Bancorp (NBBK) CEO buy shares in the latest Form 4?

The NB Bancorp (NBBK) CEO purchased shares at $20.16 each. Joseph P. Campanelli acquired 2,500 shares of common stock in an open-market transaction on March 19, 2026, raising his directly owned holdings to 396,661 shares.

How many NB Bancorp (NBBK) shares does the CEO now hold directly after this transaction?

After the reported transaction, the CEO directly holds 396,661 NB Bancorp shares. This reflects the addition of 2,500 common shares purchased on March 19, 2026 at $20.16 per share in an open-market transaction.

What indirect NB Bancorp (NBBK) shareholdings are reported for the CEO?

The CEO reports several indirect NB Bancorp (NBBK) holdings. These include 47,000 shares held by an IRA, 49,597 shares by a 401(k), 3,677 shares by an ESOP, and 3,000 shares held as trustee for a trust, in addition to his direct holdings.

Does the NB Bancorp (NBBK) CEO’s reported ownership include restricted stock?

Yes, the CEO’s reported NB Bancorp (NBBK) holdings include restricted stock. Footnotes state that some shares are restricted stock vesting 20% per year starting April 24, 2026 and 33 1/3% per year starting February 25, 2027.

Was the NB Bancorp (NBBK) CEO’s latest transaction a buy or a sell?

The latest reported transaction for NB Bancorp (NBBK) by the CEO was a buy. Joseph P. Campanelli executed an open-market purchase of 2,500 common shares at $20.16 per share on March 19, 2026.