"Mackinac" returned to Saipan in April 1945. On 11 May 1945, she joined a seaplane group based at Kerama Retto in the Ryukyu Islands during the Okinawa campaign, and continued a variety of duties, including air-sea rescue and bombardment of Japanese‑held Rose Island. After the seaplane group moved its operations to Okinawa on 14 July 1945, "Mackinac" tended motor torpedo boats through early August 1945. After the Japanese capitulation on 15 August 1945, she was assigned to join Task Group 30.5, arriving at Sagami Bay, Tokyo, Japan, on 28 August 1945.