S-7 sailed from New London, Connecticut on 18 November 1920 to rendezvous with S-boats of Submarine Division 18 (SubDiv 18) and her own division — SubDiv 12 — off New Hampshire. They proceeded via the Panama Canal to Hawaii, arriving at Pearl Harbor on 15 April 1921. Departing Pearl Harbor on 3 November, they reached Cavite, Luzon, Philippine Islands, on 1 December. This was the longest cruise on record, at that time, for American submarines.
S-7 remained at Mare Island through 1925 and operated along the West Coast in 1926, mainly at San Francisco, San Pedro Submarine Base-San Pedro, and San Diego, California. Sailing from San Francisco on 17 February 1927, she operated in the Panama Canal area from March–April, arrived at New London on 3 May, and spent the rest of the year operating along the New England coast. S-7 served in the Panama Canal area from February–April 1928, from January–April 1929, and from January–March 1930, with the remainder of those years in the northeast.