She was repurposed as a destroyer tender after the J class was removed from service in the 1920s, tasked with supporting the two O-class submarines during 1929 and 1930.

At the conclusion of the war, the ship was transferred to the Royal Australian Navy and was commissioned into the RAN on 25 March 1919.

Platypus's main role was to support the RAN's six J-class submarines, which she sailed with from Britain to Sydney between April and July 1919.

[1] The ship's commanding officer was sympathetic, promising that he would forward their concerns to the Australian Commonwealth Naval Board (which refused to consider them) and that they would not be punished.

In June 1944 Platypus received a major refit and sailed to New Guinea as a repair and maintenance vessel.