Sydney was initially used for training and a single supply run in support of Malaysia's defence policy against Indonesia, but in 1965, she sailed on the first voyage to Vũng Tàu, transporting soldiers and equipment to serve in the Vietnam War.

Despite several plans to preserve all or part of the ship as a maritime museum, tourist attraction, or car park, the carrier was sold to a South Korean steel mill for scrapping in 1975.

[2] Sydney was fitted with four Admiralty 3-drum boilers, which provided steam to Parsons single reduction geared turbines; these supplied 40,000 shp (30,000 kW) to the two propeller shafts, and allowed the ship to reach 24.8 knots (45.9 km/h; 28.5 mph).

[3][6] Although Terrible was due for completion on 24 June 1948, a skilled labour shortage affected the installation of the ship's boilers, causing the Admiralty to revise the delivery date to October 1948.

[19] A commissioning crew for the aircraft carrier was raised in Australia from the ship's company of the decommissioned cruiser Hobart, which departed from Sydney aboard HMAS Kanimbla in June 1948.

[22] The ship's sea trials and post-commissioning workup were not without event: in early December 1948, a 771 Naval Air Squadron de Havilland Mosquito crashed while helping Sydney calibrate her radar suite, killing both British aircrew, and a RAN pilot undergoing landing qualifications aboard HMS Illustrious on 17 March 1949 crashed while attempting to land: none were killed, but the pilot's Fairey Firefly and four others in the deck park were destroyed.

[24] Sydney arrived at Jervis Bay on 25 May, where the aircraft of the 20th CAG and training equipment were offloaded for transport to the new naval air station, HMAS Albatross, before the carrier proceeded to her namesake city.

[28] Before Sydney departed in late October, the British Admiralty suggested that she be deployed to the Korean War as relief for HMS Theseus and her worn-out catapult, but this was withdrawn because of the plan's drawbacks.

[5] A Firefly, a 16-foot (4.9 m) motor dinghy, and a forklift were lost overboard, six other aircraft parked on the deck were destroyed, and the carrier experienced extreme winds—the wind recorder broke after registering 68 knots (126 km/h; 78 mph).

[47] The next day, during a moderately successful strike involving five RAN aircraft against a railway tunnel, a Firefly was shot down 75 miles (121 km) inland, deep inside North Korean territory.

[49] All three aircraft were at extreme fuel limits on their return: the two Fireflies barely made it back to Sydney, while Uncle Peter arrived at Kimpo air base at 18:30 and had to land with the aid of truck headlights.

[51] Despite foul weather, the carrier's aircraft continued to attack lines of supply and communication, and provide support to United Nations ships: the 1000th combat sortie was flown on 12 November, a day before the patrol's end.

[52] Aircraft from Sydney performed strikes against coastal artillery batteries, barracks, industrial areas and railway lines, and provided a combat air patrol for the ships.

[54] Clear weather, which lasted until 14 December, allowed the carrier to maintain a high rate of attack against North Korean troop concentrations, railways, and coastal vessels, while providing air cover for the Task Element.

[54] The third RAN pilot to be lost in Korea died on 2 January while performing a combat air patrol around the carrier; personnel on the flight deck saw the aircraft fly into a cloud, but not emerge.

[54] For most of the patrol, RAN aircraft attacked artillery emplacements and concentrations of junks in the Cho Do-Sok To area, while also proving air support for South Korean Army and irregular forces.

[54] This patrol was marked by minimal flying activity due to extremely poor weather and a lack of co-ordination between UN forces and the convoys RAN aircraft were meant to escort.

[27][64] The carrier and her aircraft participated in the Coronation Fleet Review on 15 June, and visited Canada, the United States, the Caribbean, Panama, Hawaii, and New Zealand on the return voyage, before reaching Sydney on 15 August.

[69] Following an appraisal process by the RAN, during which Sydney's potential usefulness as a commando carrier, aircraft transport, or troopship was considered, the ship was paid off into Special Reserve on 30 May 1958 as surplus to requirements.

[77][78] Over several days, groups of trainee officers and sailors had been ordered to take one of the ship's whaleboats on a twelve-hour voyage around Hayman and Hooke Islands; out of the sight of both the carrier and her escort, the destroyer HMAS Anzac.

[9][81] In total, 1,245 personnel were also embarked: engineers from the 7th Field Squadron, the Royal Australian Artillery's 111th Light Anti-aircraft Battery, and four UH-1 Iroquois helicopters plus associated air- and ground crew from No.

[99][100] The three ships reached Vũng Tàu on 28 September, and departed two days later: after clearing the Market Time area, the two destroyers headed for Hong Kong, while Sydney proceeded to Subic Bay, then to her namesake city, where she arrived on 20 October.

[102] With Vampire escorting and Westland Wessex helicopters aboard for the first time, the troopship spent 20 April disembarking 7 RAR in Vũng Tàu before arriving in Singapore two days later.

[107] After this voyage, Sydney underwent an extensive refit in which she was fitted with three new Favelle Favco-type cargo cranes and modified to carry six Landing Craft Mechanized (LCM (6)) on davits.

[118] Meeting the destroyer escort Derwent en route, Sydney arrived in Vũng Tàu on 6 November, where the stores were offloaded and replaced by Australian personnel and equipment from assorted units over a two-day period.

[121] During the return voyage, Sydney encountered the disabled merchant ship Kaiwing, and towed her 450 nautical miles (830 km; 520 mi) to Hong Kong for repairs, arriving on 30 November.

[75] At the start of the year, Sydney was marked for a potential deployment to Mururoa in support of a Royal New Zealand Navy frigate sent to protest French nuclear testing at the atoll.

[131] The Australian government did not want to send a warship until all other avenues of protest had been exhausted; the length of this delay meant Supply's refit was finished before Sydney was deployed, and the oiler was sent instead.

[119] The Naval History Society of Australia suggested that the island superstructure be removed and located in The Rocks as a maritime museum, while the owners of the Sydney Opera House planned to use the ship as a floating car park.

[109][134] Following the decommissioning of Sydney, the Australian Defence Force did not possess a long-range troop transportation capability until the modified Round Table-class landing ship HMAS Tobruk was commissioned in 1981.