WESCO INTERNATIONAL INC

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 (Amendment No. )

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

WESCO INTERNATIONAL, INC.

(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 all boxes that apply):

☒ 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

2026 PROXY STATEMENTand Notice of Annual Meeting of Stockholders

WESCO INTERNATIONAL, INC.225 West Station Square Drive, Suite 700Pittsburgh, Pennsylvania 15219-1122

Notice of 2026 Annual Meeting of Stockholders

Dear Fellow Stockholders:

I am pleased to invite you to attend our 2026 Annual Meeting of Stockholders. It will be held via live audio webcast on May 28, 2026. Details regarding the items of business to be conducted at the Annual Meeting are described in the accompanying Proxy Statement:

Elect ten Directors for a one-year term expiring in 2027.

Approve, on an advisory basis, the compensation of the Company’s named executive officers.

Ratify the appointment of PricewaterhouseCoopers LLP as our independent registered public accounting firm for the year ending December 31, 2026.

Transact any other business properly brought before the Annual Meeting.

We are sending a Notice Regarding the Availability of Proxy Materials to you on or about April 17, 2026. Stockholders of record at the close of business on March 30, 2026 will be entitled to vote at our Annual Meeting or any adjournments or postponements of the meeting. You have a choice of voting online during the open poll section of the meeting, over the internet, by telephone, or by requesting a paper copy of the proxy materials and a proxy card and then executing and returning the proxy card. In order to assure a quorum, please vote over the internet or by telephone, or request a paper copy of a proxy card and then complete, sign, date and return the proxy card in the postage-paid envelope provided, whether or not you plan to attend the meeting.

Thank you for your ongoing support of Wesco.

By order of the Board of Directors,

John J. Engel

Chairman, President and Chief Executive Officer

Table of Contents

Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting of Stockholders to be Held on May 28, 2026

The 2026 Proxy Statement and 2025 Annual Report of WESCO International, Inc. (“Wesco” or the “Company”) are available to review at: www.proxydocs.com/wcc. A copy of our Annual Report on Form 10-K is available upon request, at no cost. Any request should be directed to our Corporate Secretary at the Company’s headquarters office located at 225 West Station Square Drive, Suite 700, Pittsburgh, Pennsylvania 15219-1122.