Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the year ended December 31, 2025. OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from _______________ to _______________. Commission file number: 001-41899 NB BANCORP, INC. (Exact name of registrant as specified in its charter) Maryland 93-2560883 ...

Core Viewpoint - NB Bancorp, Inc. (NBBK) reported its financial results for the final quarter of 2025, indicating that earnings missed expectations from a GAAP perspective, but there are additional factors to consider [1]. Financial Performance - The earnings report for the final quarter of 2025 showed that the company's performance did not meet market expectations [1]. Market Perspective - The financial markets are viewed as efficient, with most stocks reflecting their real current value, suggesting that the best investment opportunities may lie in less-followed stocks or those that do not accurately represent market opportunities [1].

Core Viewpoint - NB Bancorp, Inc. (NBBK) has been upgraded to a Zacks Rank 2 (Buy), indicating a positive trend in earnings estimates which is a significant factor influencing stock prices [1][3]. Earnings Estimates and Stock Price Movement - The Zacks rating system is based on changes in earnings estimates, which are strongly correlated with near-term stock price movements [4][6]. - An increase in earnings estimates typically leads to higher fair value calculations by institutional investors, resulting in buying or selling actions that affect stock prices [4]. Company Performance and Outlook - The upgrade for NB Bancorp, Inc. suggests an improvement in its underlying business, which could lead to increased stock prices as investors respond positively to this trend [5]. - The Zacks Consensus Estimate for NB Bancorp, Inc. has risen by 12.6% over the past three months, with expected earnings of $2.23 per share for the fiscal year ending December 2026, indicating no year-over-year change [8]. Zacks Rank System - The Zacks Rank system classifies stocks into five groups based on earnings estimates, with only the top 20% receiving a "Strong Buy" or "Buy" rating, indicating superior earnings estimate revisions [9][10]. - The upgrade of NB Bancorp, Inc. to a Zacks Rank 2 places it in the top 20% of Zacks-covered stocks, suggesting potential for market-beating returns in the near term [10].

Core Viewpoint - NB Bancorp, Inc. reported quarterly earnings of $0.51 per share, exceeding the Zacks Consensus Estimate of $0.49 per share, and showing an increase from $0.34 per share a year ago, representing an earnings surprise of +4.08% [1] Financial Performance - The company posted revenues of $63.15 million for the quarter ended December 2025, which missed the Zacks Consensus Estimate by 4.46%, compared to $46.3 million in revenues a year ago [2] - Over the last four quarters, NB Bancorp has surpassed consensus EPS estimates three times and topped consensus revenue estimates two times [2] Stock Performance - Since the beginning of the year, NB Bancorp shares have increased by approximately 3.3%, while the S&P 500 has gained 0.4% [3] Future Outlook - The company's earnings outlook is crucial for investors, including current consensus earnings expectations for upcoming quarters and any recent changes to these expectations [4] - The current consensus EPS estimate for the coming quarter is $0.47 on $68 million in revenues, and for the current fiscal year, it is $2.20 on $284.5 million in revenues [7] Industry Context - The Zacks Industry Rank indicates that the Banks - Northeast sector is currently in the top 33% of over 250 Zacks industries, suggesting that stocks in the top 50% outperform those in the bottom 50% by more than 2 to 1 [8]

Financial Performance - Net income for Q4 2025 was $7.7 million, or $0.19 per diluted common share, down from $15.4 million, or $0.43 per diluted common share in the prior quarter[1]. - Operating net income, excluding one-time charges, was $21.2 million, or $0.51 per diluted common share, compared to $16.0 million, or $0.45 per diluted common share in the prior quarter[1]. - Net income decreased by 49.8% to $7,707 thousand from $15,362 thousand in the previous quarter[31]. - Earnings per share (basic) fell by 55.8% to $0.19 compared to $0.43 in the previous quarter[31]. - Operating return on average assets (non-GAAP) improved to 1.35% in Q4 2025, up from 1.20% in Q3 2025 and 1.04% in Q4 2024[36]. - Operating return on average shareholders' equity (non-GAAP) increased to 10.51% in Q4 2025, compared to 8.70% in Q3 2025 and 6.98% in Q4 2024[36]. Asset and Loan Growth - Total assets increased by $1.56 billion, or 28.7%, to $7.01 billion as of December 31, 2025[7]. - Gross loans increased by $1.27 billion, or 26.9%, to $5.99 billion from the prior quarter[8]. - Total loans reached $5.99 billion as of December 31, 2025, compared to $4.72 billion in the prior quarter[28]. - Total net charge-offs for the current quarter were $4.4 million, or 0.32% of average total loans on an annualized basis, compared to $590 thousand, or 0.05% in the prior quarter[20]. - Total loans increased to $5,994,016,000 as of December 31, 2025, reflecting an organic growth of $44,464,000 or 0.9% from Q3 2025[39]. Deposit and Funding - Total deposits rose by $1.29 billion, or 28.2%, to $5.85 billion, primarily due to the acquisition of Provident's deposit portfolio[12]. - Total deposits reached $5,853,534,000, marking an increase of $199,309,000 or 4.4% from $4,565,664,000 in Q3 2025[41]. - Core deposits increased by 27.3% to $5,317,853 thousand from $4,176,991 thousand in the previous quarter[29]. Interest Income and Expenses - Net interest income for the quarter was $58.8 million, an increase of $10.6 million, or 22.0%, from the prior quarter[9]. - Total interest and dividend income rose by 19.2% to $97,362 thousand from $81,688 thousand in the previous quarter[31]. - Noninterest expense increased by $18.8 million, or 61.8%, to $49.3 million due to merger-related costs[13]. - Noninterest expense surged by 61.8% to $49,334 thousand from $30,499 thousand in the previous quarter, driven by merger and acquisition expenses[31]. Credit Quality - The allowance for credit losses (ACL) increased to $85.0 million as of December 31, 2025, or 1.42% of total loans, up from $43.1 million, or 0.91% of total loans at September 30, 2025[20]. - Non-performing loans totaled $43.4 million as of December 31, 2025, an increase of $32.0 million, or 281.9%, from $11.4 million at the end of the prior quarter[20]. - Total non-performing loans to total loans ratio rose to 0.72% as of December 31, 2025, compared to 0.24% in Q3 2025 and 0.32% in Q4 2024[37]. - The allowance for credit losses at the end of Q4 2025 was $85,009,000, significantly up from $43,052,000 in Q3 2025 and $38,744,000 in Q4 2024[38]. Mergers and Acquisitions - The company completed the acquisition of Provident for $111.8 million in cash and 5,943,682 shares valued at $114.7 million, adding approximately $1.42 billion in total assets[5]. - Total merger and acquisition expenses for the three months ended December 31, 2025, amounted to $15,740,000[42]. - Total merger and acquisition expenses for the twelve months ended December 31, 2025, were $17,265,000[42]. Dividends and Shareholder Returns - The board declared a quarterly cash dividend of $0.07 per share, payable on February 19, 2026[4]. - The company adopted a stock repurchase program for up to 2,288,509 shares, approximately 5.0% of the shares currently outstanding[3].

Financial Performance - Net income (GAAP) for the three months ended September 30, 2025, was $15.362 million, compared to $8.383 million for the same period in 2024, representing an increase of 83.5%[156] - Operating net income (non-GAAP) for the nine months ended September 30, 2025, was $44.741 million, up from $31.918 million in 2024, reflecting a growth of 40.2%[157] - Net income for the quarter ended September 30, 2025, was $15.4 million, an increase of approximately $7.0 million, or 83.3%, compared to $8.4 million for the same quarter in 2024[168] - Net income for the nine months ended September 30, 2025, was $42.6 million, an increase of approximately $16.1 million, or 60.5%, compared to the same period in 2024[187] Revenue and Income Sources - Total revenue (non-GAAP) for the nine months ended September 30, 2025, reached $150.298 million, compared to $128.296 million in 2024, an increase of 17.2%[157] - Noninterest income (GAAP) for the three months ended September 30, 2025, was $3.551 million, compared to $1.265 million in 2024, indicating a significant increase of 80.5%[157] - Noninterest income surged by $2.3 million, or 180.7%, to $3.6 million for the quarter ended September 30, 2025, primarily due to a loss on securities in the prior year[176] - Interest and dividend income rose by $23.1 million, or 10.7%, to $238.4 million for the nine months ended September 30, 2025, driven by a $23.7 million increase in interest and fees on loans[189] - Noninterest income increased by $3.8 million, or 49.6%, to $11.6 million for the nine months ended September 30, 2025, mainly from higher customer service fees and a reduction in losses on securities[196] Assets and Liabilities - Total assets increased by $284.7 million, or 5.5%, to $5.44 billion as of September 30, 2025, from $5.16 billion as of December 31, 2024[158] - Net loans increased by $378.7 million, or 8.8%, to $4.67 billion as of September 30, 2025, driven by increases in multi-family residential loans (29.2%) and commercial and industrial loans (16.4%)[161] - Total deposits rose by $388.0 million, or 9.3%, to $4.57 billion as of September 30, 2025, with core deposits increasing by $309.1 million, or 8.0%[165] - Average interest-earning assets increased by $375.0 million, or 8.0%, to $5.06 billion for the quarter ended September 30, 2025[170] - The average balance of the loan portfolio increased by $460.3 million, or 11.4%, to $4.49 billion for the nine months ended September 30, 2025[189] Expenses - Total noninterest expense increased by $5.8 million, or 23.52%, to $30.4 million for the quarter ended September 30, 2025[180] - Noninterest expense increased by $12.0 million, or 15.7%, to $88.3 million for the nine months ended September 30, 2025, with significant increases in salaries and employee benefits and data processing expenses[198] - Salaries and employee benefit expenses increased by $1.4 million, or 8.4%, primarily due to headcount increases and performance-related bonuses[179] - General and administrative expenses surged by $1.4 million, or 1,174.8%, attributed to the election of the proportional amortization method for solar income tax credit investments[180] Credit and Tax - The provision for credit losses was $1.4 million for the quarter ended September 30, 2025, down from $2.6 million in the same quarter of 2024[175] - Provision for credit losses decreased to $5.7 million for the nine months ended September 30, 2025, down from $10.7 million in the same period in 2024, reflecting improved credit quality[193] - The effective tax rate decreased to 23.0% for the quarter ended September 30, 2025, down from 45.5% in 2024[180] - The effective tax rate decreased to 24.3% for the nine months ended September 30, 2025, compared to 32.5% for the same period in 2024, primarily due to one-time tax expenses in the prior year[199] Capital and Borrowing - Total shareholders' equity decreased by $28.1 million, or 3.7%, to $737.0 million as of September 30, 2025, primarily due to a decrease in additional paid-in capital[167] - FHLB borrowings decreased by $79.4 million, or 65.7%, to $41.5 million as of September 30, 2025, reflecting overall deposit growth[166] - The company had unused borrowing capacity of $816.3 million with the Federal Home Loan Bank as of September 30, 2025[205] - The company exceeded all regulatory capital requirements and was categorized as well-capitalized as of September 30, 2025[214]

Core Insights - NB Bancorp, Inc. (NBBK) reported quarterly earnings of $0.45 per share, exceeding the Zacks Consensus Estimate of $0.42 per share, and up from $0.33 per share a year ago, representing an earnings surprise of +7.14% [1] - The company posted revenues of $51.73 million for the quarter ended September 2025, which was 1.29% below the Zacks Consensus Estimate, but an increase from $42.59 million year-over-year [2] - The stock has underperformed the market, losing about 1.6% since the beginning of the year compared to the S&P 500's gain of 14.5% [3] Earnings Outlook - The current consensus EPS estimate for the upcoming quarter is $0.44 on revenues of $53.8 million, and for the current fiscal year, it is $1.61 on revenues of $204.9 million [7] - The estimate revisions trend for NB Bancorp, Inc. was mixed ahead of the earnings release, resulting in a Zacks Rank 3 (Hold) for the stock, indicating expected performance in line with the market [6] Industry Context - The Zacks Industry Rank for Banks - Northeast places it in the top 29% of over 250 Zacks industries, suggesting that the industry outlook can significantly impact stock performance [8] - Empirical research indicates a strong correlation between near-term stock movements and trends in earnings estimate revisions, which can be tracked by investors [5]

Core Viewpoint - NB Bancorp, Inc. reported strong financial performance in Q3 2025, with net income increasing to $15.4 million, driven by growth in loans and deposits, despite a slight decline in net interest margin [1][2][4]. Financial Performance - Net income for Q3 2025 was $15.4 million, or $0.43 per diluted common share, up from $14.6 million, or $0.39 per diluted common share in the previous quarter [1][4]. - Operating net income, excluding one-time charges, was $16.0 million, or $0.45 per diluted common share, compared to $15.0 million, or $0.40 per diluted common share in the prior quarter [1][4]. - Net interest income increased to $48.2 million, a rise of $1.2 million, or 2.5%, from the previous quarter [6][20]. - Noninterest income decreased to $3.6 million, down $627 thousand, or 15.0%, from the prior quarter [8][20]. Balance Sheet Highlights - Total assets reached $5.44 billion, an increase of $215.8 million, or 4.1%, from June 30, 2025 [5][20]. - Total loans increased by $175.0 million, or 3.9%, to $4.72 billion [9][20]. - Total deposits rose by $297.6 million, or 7.0%, to $4.57 billion [9][20]. - Cash and cash equivalents increased by $36.7 million, or 14.2%, to $295.4 million [9][20]. Loan and Deposit Growth - Loans and deposits grew at annualized rates of 15.4% and 27.9%, respectively, during the third quarter [2]. - The loan-to-deposit ratio improved from 106% to 103% quarter over quarter [2]. Acquisition and Strategic Outlook - The company anticipates closing the acquisition of Provident Bancorp, Inc. in Q4 2025, which is expected to enhance growth opportunities [2][19]. - Merger and acquisition costs for the current quarter were $994 thousand, related to the Provident acquisition [9][20]. Asset Quality and Credit Losses - Provision for credit losses decreased by $1.8 million, or 55.8%, to $1.4 million for the current quarter [7][20]. - Non-performing loans totaled $11.4 million, a decrease of $1.1 million, or 9.0%, from the previous quarter [18][20]. Shareholder Returns - The Board of Directors declared a quarterly cash dividend of $0.07 per share, payable on November 19, 2025 [3].

Financial Performance - Net income for Q3 2025 was $15.4 million, or $0.43 per diluted common share, an increase from $14.6 million, or $0.39 per diluted common share in the prior quarter[1][4] - Operating net income, excluding one-time charges, was $16.0 million, or $0.45 per diluted common share, compared to $15.0 million, or $0.40 per diluted common share in the prior quarter[1][4] - Net income for the current quarter was $15,362 thousand, compared to $14,579 thousand in the previous quarter and $8,383 thousand a year ago[23] - Net income for Q3 2025 was $15,362,000, an increase of 5.4% from $14,579,000 in Q2 2025 and a significant increase from $8,383,000 in Q3 2024[31] - Operating net income (non-GAAP) for Q3 2025 reached $16,002,000, up 6.4% from $15,043,000 in Q2 2025 and 22.5% from $13,116,000 in Q3 2024[31] - Earnings per share (diluted) increased to $0.43, up 10.3% from the previous quarter and 104.8% year-over-year[26] - Operating earnings per share (non-GAAP) for Q3 2025 was $0.45, an increase from $0.40 in Q2 2025 and $0.33 in Q3 2024[31] Revenue and Income Sources - Total revenue for the current quarter was $51,726 thousand, slightly up from $51,185 thousand in the prior quarter and significantly higher than $42,589 thousand a year ago[23] - Total revenue for Q3 2025 was $51,726,000, compared to $51,185,000 in Q2 2025 and $44,457,000 in Q3 2024, reflecting a year-over-year growth of 16.4%[31] - Net interest income was $48.2 million, a 2.5% increase from $47.0 million in the prior quarter, although net interest margin declined by 4 basis points to 3.78%[7][10] - Net interest income increased to $48,175 thousand for the three months ended September 30, 2025, up from $47,007 thousand in the previous quarter and $41,324 thousand a year ago[23] - Noninterest income was $3.6 million, down by $627 thousand, or 15.0%, from the prior quarter[9] - Noninterest income totaled $3,551, a decrease of 15.0% from the previous quarter but an increase of 180.7% year-over-year[26] Asset and Liability Management - Total assets increased by $215.8 million, or 4.1%, to $5.44 billion as of September 30, 2025[5] - Total assets increased to $5,442,390 thousand as of September 30, 2025, up from $5,226,554 thousand in the previous quarter[23] - Total assets increased to $5,442,390, up 4.1% from the previous quarter and 8.8% year-over-year[24] - Total liabilities increased to $4,542,456 thousand, with shareholders' equity at $729,979 thousand[28] Loan and Deposit Growth - Gross loans rose by $175.0 million, or 3.9%, to $4.72 billion, while total deposits increased by $297.6 million, or 7.0%, to $4.57 billion[6][10] - Total deposits rose to $4,565,664, a 7.0% increase from the previous quarter and a 12.9% increase year-over-year[24] - Core deposits increased to $4,176,991, reflecting a 4.1% increase from the previous quarter and a 12.5% increase year-over-year[24] - Brokered deposits surged to $388,673, a significant 52.9% increase from the previous quarter[24] Credit Quality and Loss Provisions - Provision for credit losses decreased by $1.8 million, or 55.8%, to $1.4 million for the current quarter[8] - Provision for credit losses decreased to $1,396, down 55.8% from the previous quarter and 46.8% year-over-year[26] - The allowance for credit losses was $43.1 million, or 0.91% of total loans, compared to $42.6 million, or 0.94% of total loans at the end of the prior quarter[16] - The allowance for credit losses (ACL) was $43,052 thousand, representing 379.1% of total non-performing loans[23] - Non-performing loans decreased to $11.4 million as of September 30, 2025, down $1.1 million or 9.0% from the previous quarter[20] - Total non-performing loans decreased to $11,357,000 in Q3 2025 from $12,478,000 in Q2 2025 and $16,012,000 in Q3 2024, indicating improved asset quality[32] - Total net charge-offs for the current quarter were $590 thousand, representing 0.05% of average total loans on an annualized basis, compared to a net recovery of $19 thousand in the prior quarter[20] Efficiency and Returns - Return on average assets improved to 1.16% for the current quarter, compared to 1.13% in the previous quarter and 0.68% a year ago[23] - The efficiency ratio for the current quarter was 58.71%, slightly higher than 57.25% in the prior quarter[23] - The operating efficiency ratio (non-GAAP) was 58.22% in Q3 2025, compared to 56.22% in Q2 2025 and 57.36% in Q3 2024, indicating a slight decline in efficiency[31] - The net interest rate spread was 2.95%, slightly down from 2.96% in the previous quarter[28]

Core Viewpoint - NB Bancorp, Inc. (NBBK) has received a Zacks Rank 1 (Strong Buy) upgrade, indicating a positive outlook based on rising earnings estimates, which significantly influence stock prices [1][3]. Earnings Estimates and Stock Price Impact - The Zacks rating system is based on changes in earnings estimates, which are strongly correlated with near-term stock price movements [4][6]. - An increase in earnings estimates typically leads to higher fair value calculations by institutional investors, resulting in stock price movements [4]. Company Performance Indicators - For the fiscal year ending December 2025, NB Bancorp, Inc. is expected to earn $1.61 per share, unchanged from the previous year, but the Zacks Consensus Estimate has increased by 8.8% over the past three months [8]. - The upgrade to Zacks Rank 1 places NB Bancorp in the top 5% of Zacks-covered stocks, suggesting potential for market-beating returns in the near term [10]. Zacks Rank System Overview - The Zacks Rank system classifies stocks into five groups based on earnings estimates, with a historical average annual return of +25% for Zacks Rank 1 stocks since 1988 [7]. - The system maintains a balanced distribution of ratings, ensuring that only the top 5% of stocks receive a "Strong Buy" rating, reflecting superior earnings estimate revisions [9][10].