After shakedown off Bermuda, Knapp departed Boston on 26 November 1943 for the Pacific Ocean, arriving Pearl Harbor on 21 December.

She departed Pearl Harbor on 16 January 1944 with the aircraft carriers of Admiral Marc Mitscher's Task Force 58, headed for the Marshall Islands invasion.

Knapp steamed out of Eniwetok for the invasion of the Palau Islands on 30 August, screening five battleships and later rendezvousing with Langley, Lexington, Essex and Princeton before their strikes at targets in the Palaus during actions on Peleliu.

From November 1944 to January 1945, Knapp screened airstrikes on Luzon, French Indochina and cities on the China coast neutralizing Japanese bases in preparation for the Lingayen invasion.

Shortly after Knapp sailed via the Panama Canal for Boston arriving 17 January 1946, then Charleston, South Carolina, on 2 April and was decommissioned 5 July 1946.

She cruised in the Caribbean Sea from 20 July to 13 September when she pulled into Charleston, where she was refitted with modern equipment then sailed 4 February 1952 with a task force to England, Norway, and Germany.

Knapp transited the Straits of Gibraltar on 26 January 1953 and overhauled at Boston until 10 August 1953, when she deployed with Destroyer Division 182 for a world cruise.

She patrolled the Korean coast with Task Force 77 until 14 January 1954 when she resumed her cruise via Hong Kong, Singapore, Colombo, Aden, Saudi Arabia, Suez Canal, visited Port Said, Naples, Barcelona, Lisbon, Bermuda and arrived Fall River, Massachusetts, on 10 March 1954.