After the United States entry into World War I on 6 April 1917, "Porter" was readied for overseas duty and departed from New York on 24 April with the other five ships of her division— (the flagship), , , , and . The sextet arrived at Queenstown, Ireland, on 4 May and began patrolling the southern approaches to the Irish Sea the next day. Based at Queenstown, "Porter" met and escorted convoys from the United States as they entered the war zone.