Exhibit 15

October 27, 2017

Securities and Exchange Commission

100 F Street, NE

Washington, D.C. 20549

RE: Alcoa Corporation

Commissioners:

We are aware that our report dated October 27, 2017 on our review of interim financial information of Alcoa Corporation and its subsidiaries (Alcoa Corporation) for the three- and nine-month periods ended September 30, 2017 and 2016 and included in Alcoa Corporation’s quarterly report on Form 10-Q for the quarter ended September 30, 2017 is incorporated by reference in its Registration Statements on Form S-8 (Nos. 333-214420, 333-214423, and 333-218038).

Very truly yours,

/s/ PricewaterhouseCoopers LLP

PricewaterhouseCoopers LLP

Pittsburgh, Pennsylvania