On 15 August 1945, "I-203" was at Maizuru, Japan, with her sister ships and when she was reassigned to Submarine Division 15 in the 6th Fleet. The same day, hostilities between Japan and the Allies came to an end. Japan formally surrendered in a ceremony aboard the United States Navy battleship in Tokyo Bay on 2 September 1945, and "I-203" surrendered to the Allies at Maizuru that day.