Company: NWBI
Filing Date: 2025-02-24
Form Type: 424B3
Source: 0001193125-25-033488
Chunk: 4

Company: Northwest Bancshares, Inc.
Filing Date: 2025-02-24
Form: 424B3
Chunk 4
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|                   |     | By Order of the Board of Directors, |
|                   |     | Richard A. Grafmyre                 |
|                   |     | Chief Executive Officer             |
| February 24, 2025 |     | Penns Woods Bancorp, Inc.           |

WHERE YOU CAN FIND MORE INFORMATION Northwest Bancshares, Inc. (“Northwest”) and Penns Woods Bancorp, Inc. (“Penns Woods”) are publicly traded companies that file annual, quarterly and other reports, proxy statements and other business and financial information with the Securities and Exchange Commission (the “SEC”). Our public filings are available to the public from the SEC’s website at www.sec.gov. You may request a copy of our filings with the SEC (excluding exhibits) at no cost by contacting us at the address and/or telephone number below. Certain information filed by Northwest with the SEC is also available, without charge, through Northwest’s website at www.Northwestbancorp.com under the “Investor Relations” section. Northwest has filed with the SEC a registration statement on Form S-4to register its common stock to be issued to Penns Woods shareholders as the merger consideration. This document is a part of that registration statement. As permitted by SEC rules, this document does not contain all of the information included in the registration statement or in the exhibits or schedules to the registration statement. You may read and request a copy of the registration statement, including any amendments, schedules and exhibits at the addresses set forth below. Statements contained in this document as to the contents of any contract or other documents referred to in this document are not necessarily complete. In each case, you should refer to the copy of the applicable contract or other document filed as an exhibit to the registration statement. This proxy statement/prospectus incorporates by reference important business and financial information about Northwest and Penns Woods from documents filed with the SEC that are not included in or delivered with this proxy statement/prospectus. See “ INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE” beginning on page 89. These documents are available, without charge, to you upon written or oral request at the applicable company’s address and telephone number listed below:

| Northwest Bancshares, Inc.        
 3 Easton Oval Street Suite 500    
 Columbus, Ohio 43219 Attention:   
 Investor Relations (814) 726-2140 |     | Penns Woods Bancorp, Inc.             
 300 Market Street P.O. Box 967        
 Williamsport, Pennsylvania 17703-