[Form 4] NB Bancorp, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Kenneth C. Montgomery, a director of NB Bancorp, Inc. (NBBK), purchased 5,000 shares of the company's common stock on 09/12/2025 at a reported price of $18.44 per share, increasing his total beneficial ownership to 80,337 shares. The reported total includes restricted stock that vests at a rate of 20% per year beginning on April 24, 2026, indicating portions of the holdings are subject to future vesting rather than immediate sale.

The Form 4 reports a direct acquisition and shows no derivative transactions or dispositions. The filing was submitted under power of attorney on behalf of the reporting person.

Insights

Financial Analyst

TL;DR: A director made a modest open-market purchase of 5,000 shares, increasing direct ownership to 80,337 shares.

The transaction is a straightforward insider purchase at $18.44 per share, representing a direct increase in beneficial ownership. The addition is documented as common stock with no options or derivative activity disclosed. The inclusion of restricted shares that vest 20% annually from April 24, 2026 means a portion of the reported holdings cannot be sold immediately. Given the single-line disclosure and absence of material derivative activity, this filing constitutes routine insider activity rather than a material corporate event.

Corporate Governance Expert

TL;DR: Director purchase recorded; vesting schedule for restricted stock is disclosed, no governance red flags evident.

The Form 4 transparently reports direct ownership and the vesting terms for restricted stock, which is relevant for understanding liquidity and potential future share availability. There are no indications of sales, pledges, or related-party transactions in this filing. The report was executed via power of attorney, a common procedural step. Overall, the disclosure aligns with standard Section 16 reporting obligations and raises no immediate governance concerns based on the information provided.

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

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

1. Name and Address of Reporting Person^*

Montgomery Kenneth C.

(Last) (First) (Middle)

1063 GREAT PLAIN AVE

(Street)

NEEDHAM MA 02492

(City) (State) (Zip)

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
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
09/12/2025

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

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

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

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	09/12/2025		P		5,000	A	$18.44	80,337(1)	D

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.

	/s/ Steven Lanter, pursuant to power of attorney	09/15/2025
	** 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).
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