Company: EVF
Filing Date: 2025-09-23
Form Type: DEFA14A
Source: 0001133228-25-010015
Chunk: 0

Company: Eaton Vance Senior Income Trust
Filing Date: 2025-09-23
Form: DEFA14A
Chunk 0
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<div align='center'>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</div>

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 |

<div align='center'>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)</div>

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                                                                                   |

<div align='center'>Eaton Vance Senior Income Trust

One Post Office Square

Boston, Massachusetts 02109

Supplement to Proxy Statement

for

Annual Meeting of Shareholders</div>

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.

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