After the declaration of war in Korea, Canada ordered three destroyers of the Pacific Division based at CFB Esquimalt to begin preparations for deployment to the Korean theatre. "Sioux" was in dry dock and not expected to leave it until 30 June 1950. However, after a massive effort by the dockside crews, "Sioux" departed with "Cayuga" and on 5 July 1950. The three vessels arrived at Sasebo on 30 July 1950. After arriving, the destroyer was assigned to Task Force 96.5 with "Athabaskan" escorting convoys of ships from Japan to Pusan. Initially retained at Sasebo for rescue missions, on 12 August 1950, the ship transferred to Task Unit 96.53.3 assigned to the west coast of Korea.