Company: NWBI
Filing Date: 2025-02-24
Form Type: 424B3
Source: 0001193125-25-033488
Chunk: 214

Company: Northwest Bancshares, Inc.
Filing Date: 2025-02-24
Form: 424B3
Chunk 214
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A-60

AGREEMENT AND PLAN OF MERGER Signature Page IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be executed in counterparts by their duly authorized officers, all as of the day and year first above written.

| PENNS WOODS BANCORP, INC. |     |                          |
| By                        |     | /s/ Richard A. Grafmyre  |
|                           |     | Richard A. Grafmyre, CEO |

| NORTHWEST BANCSHARES, INC. |     |                                     |
| By                         |     | /s/ Louis J. Torchio                |
|                            |     | Louis J. Torchio, President and CEO |

A-61

Exhibit A

Form of Support Agreement

See attached.

A-62

SUPPORT AGREEMENT

THIS SUPPORT AGREEMENT (this “”), is entered into as of , 2024, by
and among Northwest Bancshares, Inc., a bank holding company incorporated under Maryland law (“”), Penns Woods Bancorp, Inc., a bank holding company incorporated under Pennsylvania law (“”), and
(“”).

WHEREAS, concurrently with the execution and delivery of
this Agreement, NWBI and PWOD are entering into an Agreement and Plan of Merger, dated as of the date of this Agreement (as amended or supplemented from time to time, the “”), pursuant to which, among other things,
PWOD shall be merged with and into NWBI, upon the terms and subject to the conditions set forth in the Merger Agreement. Capitalized terms not otherwise defined in this Agreement shall have meanings provided in the Merger Agreement.

WHEREAS, as of the date of this Agreement, Shareholder is the record or beneficial owner of, and has the power to vote, the number of
shares of PWOD Common Stock set forth, and in the manner reflected, on (the shares listed on, together with all shares of PWOD Common Stock subsequently acquired by the Shareholder during the term of
this Agreement, are referred to in this Agreement as the “”).

WHEREAS, as an inducement and condition
to entering into the Merger Agreement, NWBI has required that Shareholder agree, and Shareholder has agreed, to enter into this Agreement.

NOW, THEREFORE, in consideration of the foregoing and the mutual covenants and agreements contained herein, and intending to be legally
bound hereby