Following shakedown in Chesapeake Bay, "Oceanus" departed Norfolk, Virginia on 23 July 1943 for the Pacific, arriving at Nouméa, New Caledonia 18 September. She remained there, converting LCIs to shoal-draft gunboats and making emergency repairs to damaged vessels. On 28 October, she shifted to Espiritu Santo, thence, departing on 1 July 1944, to Florida Island. On 9 September 1944, she departed the Solomon Islands in TG 31.4 and on 20 September, arrived at Kossol Roads, Palaus. There she repaired, often while underway, craft and vessels damaged in the assaults against those islands and against the Philippines. In February 1945, she steamed to Guam to join TG 51.5 for the Iwo Jima invasion, arriving on 20 February, and remaining until 17 March.