Arch Capital (ACGL) 10-Q 2018 Q2 Quarterly report

Exhibit 15

August 8, 2018

Securities and Exchange Commission

100 F Street, N.E.

Washington, DC 20549

Commissioners:

We are aware that our report dated August 8, 2018 on our review of interim financial information of Arch Capital Group Ltd., which appears in this Quarterly Report on Form 10-Q, is incorporated by reference in the Registration Statements on Form S-3 (Nos. 333-221344, 333-221344-01 and 333-221344-02) and in the Registration Statements on Forms S-8 (Nos. 333-99974, 333-86145, 333-82772, 333-211193, 333-72182, 333-98971, 333-124422, 333-142835, 333-181308, 333-203993 and 333-224783) of Arch Capital Group Ltd.

Very truly yours,

/s/ PricewaterhouseCoopers LLP

PricewaterhouseCoopers LLP

New York, NY