Additional Proxy Soliciting Materials (Form DEFA14A)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

☐	Preliminary Proxy Statement

☐	Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☐	Definitive Proxy Statement

☒	Definitive Additional Materials

☐	Soliciting Material Pursuant to §240.14a-12

Eaton Vance Senior Income Trust

(Name of Registrant as specified in its Charter)

(Name of Person(s) Filing Proxy Statement), if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

☒	No fee required.

☐	Fee paid previously with preliminary materials.

☐	Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11

Eaton Vance Senior Income Trust

One Post Office Square

Boston, Massachusetts 02109

Supplement to Proxy Statement

for

Annual Meeting of Shareholders

On August 22, 2025, Eaton Vance Senior Income Trust (the "Fund") filed with the Securities and Exchange Commission the definitive proxy statement (the "Proxy Statement") for its annual meeting of shareholders (the "Annual Meeting") to be held on Wednesday, October 8, 2025, at 11:30 a.m. (Eastern Time). The Fund is filing this supplement to its Proxy Statement (the "Supplement") to correct certain inadvertent scrivener's errors in the Proxy Statement and the form of proxy cards filed with the Proxy Statement, as discussed below.

1.

The Proxy Statement referenced an incorrect number of outstanding Auction Preferred Shares entitled to vote at the Annual Meeting as of the record date, July 29, 2025. We are issuing this Supplement to provide the correct information:

As of July 29, 2025, there were 1,504 Auction Preferred Shares, $0.01 par value per share, liquidation preference $25,000 per share, of the Fund outstanding.

2.

The form of proxy cards attached to the EDGAR filing referenced an incorrect Annual Meeting date. The proxy cards mailed to shareholders included the correct Annual Meeting date, and this Supplement updates the form of proxy cards included in the EDGAR version of the Proxy Statement. There are no changes to the proxy card or voting instruction form previously mailed to shareholders.

For more information, please contact the Fund at 1-800-262-1122. This Supplement should be read in conjunction with the Proxy Statement, and other than the revisions described above, this Supplement does not modify any information in the Proxy Statement. From and after the date of this Supplement, any references to the "Proxy Statement" are to the Proxy Statement as supplemented hereby.

September 23, 2025

48648-00 9.23.25