Following the Attack on Pearl Harbor he was called to active duty and reported on 9 January 1942 to fleet oiler USS Neosho.

Her first port availability period at Manus, Admiralty Islands, was marked on 10 November by the explosion of the Mount Hood (AE-11) an ammunition ship nearby.

She returned to Ulithi on 14 January 1945, but again early in February was at sea protecting a replenishment group during the capture of Iwo Jima.

Underway again on 3 July, the destroyer escort ended the war guarding the supply ships of the 3rd Fleet, then striking the Japanese home islands.

Lyman was the first DE to enter Tokyo Bay on 30 August with a group of tankers, she remained to witness the surrender ceremony of 2 September.