Soon after fitting out and shakedown, Nahma reported to Gibraltar to join a group of American vessels based there and serving as convoy escorts. With these ships, she escorted vessels in the Mediterranean, as well as between the UK and Gibraltar until the end of World War I. Following the Armistice she remained in the Mediterranean for relief and quasi-diplomatic work. Operating in the Aegean and Black Seas she carried relief supplies to refugee areas; evacuated American nationals, non-combatants, the sick, and the wounded from civil war torn areas of Russia and Turkey; and provided communications services between ports. She was decommissioned at Greenock, Scotland, on 19 July 1919, and was returned to her owner.