Duncan, converted to a radar picket destroyer during her post-shakedown overhaul, sailed from Norfolk on 2 June 1945 for the Pacific, and after touching down at San Diego and Pearl Harbor, joined Cabot (CVL-28) for screening and plane guard duty during the strikes on Wake Island of 1 August.

After calling at Eniwetok, she continued to Okinawa to join the 7th Fleet for patrol duty off the Chinese and Korean coasts during the landing of occupation troops at Tsingtao, Taku, and Incheon.

"[1] After repairs at Long Beach, California, the destroyer rejoined the fleet for training until January 1949, when she again sailed for the western Pacific, this time for eight months.

After the end of the Korean fighting in 1953, Duncan remained busy in the Pacific, alternating Far Eastern duty with training and maintenance on the west coast.

During the Vietnam War Duncan served as plane guard for aircraft carriers on "Yankee Station" in the Gulf of Tonkin, participated in Operations "Sea Dragon" and "Market Time", patrolled on search and rescue duties, and carried out naval gunfire support missions.