After the war, O-6 prolonged her Naval career by operating as a training ship out of New London, Connecticut. Reclassified to a second line submarine on 25 July 1924 while stationed at Coco Solo in the Panama Canal Zone, she reverted to first line class on 6 June 1928 and continued at New London until February 1929, when she steamed to Philadelphia, Pennsylvania, to decommission there on 9 June 1931.
Remaining in the Portsmouth area, O-6 decommissioned there on 11 September 1945, was struck from the Naval Vessel Register the same day, and was sold to John J. Duane Company of Quincy on 4 September 1946. The boat was subsequently scrapped in December 1946.
The American Campaign Medal was awarded for For thirty days service outside the Continental United States but within the American Theater of Operations between December 7, 1941, and March 2, 1946; or,
... More an aggregate service of one year within the Continental United States during the same period under the following circumstances: On permanent assignment outside the continental limits of the United States; or, On permanent assignment as a member of a crew of a vessel sailing ocean waters for a period of 30 consecutive days or 60 non-consecutive days; or, For service outside the continental limits of the United States in a passenger status or on temporary duty for 30 consecutive days or 60 non consecutive days; or, For service in active combat against the enemy and awarded a combat decoration or furnished a certificate by the commanding general of a corps, higher unit, or independent force that the individual actually participated in combat; or, For service within the continental limits of the United States for an aggregate period of one year. Hide