Duncan sailed along the East Coast and in the Caribbean for training, target practice and exercises until 24 October 1914, when she was placed out of commission at Boston. Recommissioned on 22 January 1916, she sailed out of Hampton Roads and Newport for neutrality patrol and exercises in the Caribbean, protecting battleships in fleet maneuvers, and guarding the entrance to the York River. Between 8 and 30 September 1917, she escorted a convoy to an eastern rendezvous, where an escort out of England met the ships.
Sailing for New York on 30 October, Duncan escorted a convoy to Brest, France, arriving at Queenstown, Ireland on 15 November to escort convoys and hunt submarines in the Irish Sea. On 17 July 1918, Duncan rescued from a small boat the survivors of the Norwegian bark Miefield and on 9 October, when one of her sisters, Shaw (Destroyer No. 68) collided with SS Aquitania, Duncan took off 84 of her crew, 12 of them wounded, and stood by while Shaw’s remaining men took their ship into Portland, England, under her own power.
Remaining in European waters after the war, Duncan joined in escorting George Washington, bearing President W. Wilson, into Brest 13 December 1918. She cleared Queenstown on 26 December for the Azores, Bermuda, and Norfolk, arriving 12 January 1919. After five months of East Coast and Caribbean operations, she was placed in ordinary at Norfolk on 31 May 1919; in reduced commission on 1 January 1920; in reserve on 1 August 1920; assigned to operate with 50 percent of her complement on 1 January 1921; and decommissioned on 9 August 1921. She was scrapped on 8 March 1935 in accordance with the terms of the London treaty limiting naval armaments.