Over the next five months, Allen conducted patrol and escort duty along the eastern seaboard and in the West Indies. During that time, the United States entered World War I on the side of the Allies on 6 April.
On 14 June, the destroyer put to sea from New York in the escort of one of the first convoys to take American troops to Europe. After seeing the convoy safely across the Atlantic, Allen joined other American destroyers at Queenstown, Ireland, and began duty patrolling against U-boats and escorting convoys on the last leg of their voyage to Europe. That duty included escort missions into both French and British ports. During her service at Queenstown, she reported engagements with German submarines on 10 separate occasions, but postwar checks of German records failed to substantiate even the most plausible of the supposed encounters.
One of the last duties the destroyer performed in European waters came in December 1918 when she helped to escort George Washington—with President Woodrow Wilson embarked—into Brest, France, on the 13th. Following that mission, the destroyer returned to Queenstown, whence she departed on the day after Christmas, bound for home. Allen stood into New York on 7 January 1919.
After voyage repairs, the destroyer resumed duty along the East Coast and in the West Indies with the Atlantic Fleet. That duty continued until 22 June 1922 at which time she was placed out of commission, in reserve. She was placed back in commission three years later, on 23 June 1925, and spent almost three years as a training platform for naval reservists at Washington, D.C. In March of 1928, the destroyer returned to the Reserve Fleet and was berthed at Philadelphia. There, she remained for more than 12 years.
On 23 August 1940, Allen was recommissioned at Philadelphia, Lt. Comdr. Frederick P. Williams in command. Following a brief period of service on the East Coast, she was reassigned to the Pacific Fleet as a unit of Destroyer Division (DesDiv) 80. By the time Allen returned to commission, the Pacific Fleet had been moved from its base on the west coast to Pearl Harbor in Hawaii as a gesture to “restrain” the Japanese. Therefore, Allen moved to the Hawaiian base whence she operated until the beginning of hostilities between the United States and Japan.
On the morning of 7 December 1941, Allen was moored in East Loch to the northeast of Ford Island and just south of east of the hospital ship Solace (AH 5). During the Japanese attack on the harbor, she claimed to have assisted in downing three enemy planes.
Following the attack, Allen began duty escorting ships between islands of the Hawaiian chain and patrolling the area for enemy ships—primarily submarines. She also made periodic round trip voyages to the West Coast. Such duty remained her occupation throughout World War II.
In September 1945, the destroyer sailed from Hawaii to Philadelphia, where she was placed out of commission on 15 October 1945. Her name was struck from the Navy list on 1 November 1945, and she was sold to the Boston Metals Co., Baltimore, on 26 September 1946 for scrapping.
Allen earned one service star on her Asiatic-Pacific campaign medal.