Built by Scottish shipbuilder Harland and Wolff and completed in 1929, Westralia was operated by the Huddart Parker company until 1939, when she was requisitioned for service with the RAN as an Armed Merchant Cruiser (AMC).

Before she could be returned to her owners, the vessel was requisitioned again, this time for use as a troop transport supporting the British Commonwealth Occupation Force (BCOF).

Westralia was built at the Harland and Wolff shipyard in Govan for the Huddart Parker company as a twin screw motor vessel.

[3][5] Westralia's time as an AMC was spent escorting convoys in the Pacific and Indian oceans, primarily from Australia and New Zealand.

[9] After sailing to Cairns for replenishment (most of the commissaries in Darwin had been drained to supply Australian and Dutch forces securing the Dutch East Indies against a pending Japanese invasion), the sailors had to work all day to disembark the troops, and when the planned evening departure was cancelled because the ship's floatplane could not be reembarked, shore leave was not granted.

[10] Westralia arrived in Darwin on 30 December, then was ordered to Sydney so an inquiry into the incident could be held: the records relating to the legal proceedings and punishments have been lost.

[14][15] Westralia sailed from Japan via Rabaul for Brisbane, due about 17 July 1946, and thereafter Sydney where she was to be converted to coastal passenger service.

[16] However, as she was being refitted for a return to civilian service, Westralia was taken up again for use as a troop transport between Sydney and Kure for the British Commonwealth Occupation Force (BCOF).

[2] She ended her time with the BCOF in April 1949, then was chartered as a troop carrier by the British Ministry of Transport, and served in the Mediterranean until March 1950.