Exhibit 10.1

November 28, 2025

3i, LP
2 Wooster Street, 2nd Floor,
New York, New York 10013.
Attn: Maier Joshua Tarlow, Manager of 3i Management, LLC, the general partner of 3i, LP

Dear Sirs:

Reference is made to (a) that certain Securities Purchase Agreement dated as of July 29, 2025 (the “Purchase Agreement”) between Capstone Holding Corp. (the “Company”) and the purchaser identified therein (the “Investor”), (b) that certain convertible note in the original principal amount of approximately $3,272,966 with a 8.34% original issue discount issued to the Investor (the “July 2025 Convertible Note”), (c) that certain convertible note was issued in the original principal amount of approximately $3,545,712.42 with a 8.34% original issue discount issued to the Investor (the “October 2025 Convertible Note,” and together with the July 2025 Convertible Note, the “Notes”), and (d) the other transaction documents, as modified from time to time, referred to collectively, as the “Transaction Documents”. Capitalized terms used but not defined herein shall have the meanings given to them in the Purchase Agreement, or if not defined therein, in the Note, or if not defined therein, in the applicable Transaction Document, in each case as of the date hereof.

This letter agreement (this “Letter Agreement”) confirms our recent discussions about, among other matters, certain modifications to the Note.

Pursuant to Section 7(h) of the Notes, starting on November 28, 2025 through the Maturity Date of each Note, the Company hereby reduces the Conversion Price of the Notes to $0.75 with regard to the entire amount of the July 2025 Convertible Note still owed and with regard to $1,772,856.21 of the principal amount of the October 2025 Convertible Note (with $1,772,856.21 of the principal balance of the October 2025 Convertible Note still having a $1.10 conversion price). Any conversion which occurs shall be voluntary at the election of the Investor, which shall evidence its election as to the Note being converted in writing on a conversion notice.

This Letter Agreement is a Transaction Document and is limited as written. As of the date first written above, each reference in the Purchase Agreement or any other applicable Transaction Document to “this Agreement,” “hereunder,” “hereof,” “herein,” or words of like import, and each reference in the other Transaction Documents to such Purchase Agreement or other Transaction Documents (including, without limitation, by means of words like “thereunder,” “thereof” and words of like import), shall refer to the Purchase Agreement as modified thereby, and this Letter Agreement and the Purchase Agreement shall be read together and construed as a single agreement. The execution, delivery and effectiveness of this Letter Agreement shall not, except as expressly provided herein, (A) waive or modify any right, power or remedy under, or any other provision of, any Transaction Document or (B) commit or otherwise obligate the Investor to enter into or consider entering into any other amendment, waiver or modification of any Transaction Document.

All communications and notices hereunder shall be given as provided in the Transaction Documents. This Letter Agreement (a) shall be governed by and construed in accordance with the law of the State of New York, (b) is for the exclusive benefit of the parties hereto and the beneficiaries of the Purchase Agreement and, together with the other Transaction Documents, constitutes the entire agreement of such parties, superseding all prior agreements among them, with respect to the subject matter hereof, (c) may be modified, waived or assigned only in writing and only to the extent such modification, waiver or assignment would be permitted under the Transaction Documents (and any attempt to assign this Letter Agreement without such writing shall be null and void), (d) is a negotiated document, entered into freely among the parties upon advice of their own counsel, and it should not be construed against any of its drafters and (e) shall survive the satisfaction or discharge of the amounts owing under the Transaction Documents. The fact that any term or provision of this Letter Agreement is held invalid, illegal or unenforceable as to any person in any situation in any jurisdiction shall not affect the validity, enforceability or legality of the remaining terms or provisions hereof or the validity, enforceability or legality of such offending term or provision in any other situation or jurisdiction or as applied to any person.

This Letter Agreement is expressly conditioned on the following conditions precedent:

Kindly confirm your agreement with the above by signing in the space indicated below and by PDFing a partially executed copy of this letter to the undersigned, and which may be executed in identical counterparts, each of which shall be deemed an original but all of which shall constitute one and the same agreement.