Following the fall of the Netherlands East Indies K IX escaped to Fremantle, Western Australia, arriving on 13 March 1942.

[2] In May 1942 the Dutch government offered K IX to the Royal Australian Navy for use in anti-submarine warfare training.

[3] Due to the boat's poor mechanical condition HMAS K9 saw little service with the RAN and spent most of her time in commission under repair.

Due to a lack of spare parts the submarine was decommissioned on 31 March 1944,[2] having spent only 31 days at sea.

K9 was washed ashore near Seal Rocks, New South Wales on 8 June 1945 while under tow to Merauke in Dutch New Guinea and subsequently stripped for scrap.