Capitán Prat served in the fleet for about ten years, until she was disarmed in accordance with a treaty signed with Argentina intended to stop a naval arms race between the two countries. The ship returned to service, however, and remained on active duty with the fleet until 1926, when she was reduced to a coastal defense ship. In 1928–1930, she was used as a submarine tender, and in 1935, she was disarmed and used as a training ship for engineers. She remained in the Navy's inventory until 1942, when she was sold for scrap.