The ships carried 225 long tons (229 t) of fuel oil which was intended gave them a range of 2,500 nautical miles (4,600 km; 2,900 mi) at 20 knots (37 km/h; 23 mph).

Assigned to U.S. patrol squadrons based on Gibraltar, Dyer sailed from New York 9 July 1918 with Assistant Secretary of the Navy Franklin Delano Roosevelt embarked for transportation to Plymouth, England.

On 4 August she began her service as escort for merchant convoys and Army transports between Gibraltar and Marseilles, France, making nine such voyages until the end of hostilities.

Naval Forces in the central and eastern Mediterranean, and called at Split and Kotor, Dalmatia (today in Croatia and in Montenegro), and Brindisi, Italy, Constantinople, Turkey, and Beirut, Lebanon, before arriving at Venice 5 February.

Operating from Venice as flagship for the force, Dyer took part in relief activities in the Balkans and Middle East, carried passengers and supplies in the Adriatic and aided in the execution of the terms of the Austrian Armistice until 16 April, when she sailed for the United States.