After the completion of her overhaul, "I-171" spent the winter, spring, and much of the summer of 1943 involved in the Aleutian Islands campaign, which had begun in mid-1942. On 15 February 1943, she left Kure to carry supplies to the Japanese garrison on Kiska in the Aleutian Islands, arriving there on 26 February 1943. She departed Kiska on 2 March 1943 and proceeded to Paramushiro in the Kuril Islands, where she arrived on 18 March 1943. After refueling from the oiler on 20 March 1943, she departed Paramushiro on her fifth war patrol, operating in the Bering Sea in the vicinity of as part of a submarine scouting line. After an uneventful patrol there, she returned to Japan, arriving at Yokosuka on 6 April 1943. Her squadron, Submarine Squadron 12, was assigned to the 5th Fleet′s Northern District Force on 13 May 1943.