While "I-1" was at Yokosuka, the Aleutian Islands campaign began on 3–4 June 1942 with a Japanese air raid on Dutch Harbor, Alaska, followed quickly by the unopposed Japanese occupation in the Aleutian Islands of Attu on 5 June and Kiska on 7 June 1942. On 10 June 1942, "I-1", "I-2", "I-3", "I-4", "I-5", "I-6", and "I-7" were reassigned to the Northern Force for duty in the Aleutians, and on 11 June 1942 "I-1" set out for Aleutian waters in company with "I-2", "I-3", "I-4", and "I-7" to begin her fourth war patrol. On 20 June 1942, "I-1", "I-2", and "I-3" joined the "K" patrol line in the North Pacific Ocean between and . In mid-July 1942, an unidentified American warship—possibly the United States Coast Guard cutter —attacked "I-1" in the North Pacific Ocean south of Adak Island and pursued her for 19 hours before "I-1" finally dived to and escaped. On 20 July 1942, "I-1" was reassigned to the Advance Force and received orders that day to return to Yokosuka, which she reached on 1 August 1942.