During the mid-1960s, the United States government pressured Australia to increase the resources it was committing to the Vietnam War; one of the requests was for a combat vessel to help the USN meet the demand for naval gunfire support operations.

[24] After a comprehensive familiarisation period, Hobart replaced USS Fechteler on 31 March, taking over the US destroyer's gunfire support duties.

[28] Several explosions in 5-inch/54 gun mounts during the later weeks of April saw all equipped destroyers (including Hobart) reassigned to other duties while investigations into the cause (believed to be a bad batch of ammunition) were explored.

[31] Apart from a brief stint on the gunline, Hobart remained assigned to Sea Dragon until 26 May, when sailed to Subic for maintenance, with both 5-inch gun barrels replaced.

[33] A reduction in the number of seaborne infiltration attempts and the increasing availability of spotter aircraft meant that most gunfire missions were against inland targets like truck convoys.

[1] Personnel awards included a Distinguished Service Order, a British Empire Medal, a Mention in Despatches and 25 Naval Board commendations.

[40] The ships were unsuccessfully shelled by coastal artillery on 22 and 23 April, then spent the next three days attempting to attract attention from shore batteries so they could be bombed by aircraft.

[40] Hobart's participation in Sea Dragon ended in late April, and after maintenance in Hong Kong and Taiwan from 1 to 20 May, resumed gunline duties.

[42] During this deployment, boat traffic between the mainland and Tiger Island was seen as a priority, with gunline ships also granted approval to operate against targets in this area.

[43] During the evening of 16–17 June, the three destroyers were ordered to undertake surveillance missions around Tiger Island, because of reports of North Vietnamese helicopter activity in the area.

[50] After being relieved, Hobart sailed for Subic Bay, where the damage was inspected by RAN and USN personnel, including three admirals.

[54][55] F-4 Phantoms of the USAF Seventh Air Force, responding several hours after the attack on the PCFs, were unable to distinguish between the radar signature of surface ships and airborne helicopters and instead opened fire on Hobart, Boston, and Edson.

[57] Although Hobart was asked to rotate Sea Dragon duties on 2 August to relieve a destroyer experiencing gunnery faults, nine days early, the destroyer's captain refused, as he wanted more time to prepare the ship after the repairs, particularly as the air warning radars were yet to become operational, and the gun mounts were experiencing minor problems.

[58] The Sea Dragon deployment did not eventuate, and after operating near the DMZ, Hobart was reassigned to gunfire support duties around southern Vietnam on 12 August.

[64] Three days later, the destroyer rammed and sank a South Vietnamese fishing craft, but rescued the five crew and transported them to shore.

[67] The ship returned to the gunline on 9 July, and operated until 29 August, when she sailed to Singapore for maintenance, then Bangkok for naval exercises.

[68] Returning on 13 September, Hobart was called to relieve USS Lloyd Thomas on the gunline after an explosion in one of the American destroyer's gun mounts.

[4] While in her namesake city, Hobart was visited by Charles, Prince of Wales; the first time the royal had boarded an Australian warship.

[4][74] Later in the year, the destroyer participated in the multinational exercise RIMPAC 75, then embarked on a three-month deployment in the Indian Ocean, during which Hobart became the first RAN ship to visit Malé in the Maldives, and the first warship to dock at HMAS Stirling, the new naval base in Western Australia.

[4] Between May and September 1976, Hobart sailed on a round-the-world voyage; the 109-day deployment was named Exercise Phineas Fogg after the main character from Around the World in Eighty Days.

During this voyage, the ship visited nineteen ports in twelve countries, and represented Australia at the fleet review off New York City commemorating the United States Bicentennial.

[4] In July 1979, Hobart and the Antarctic Support Vessel Thala Dan were sent to Macquarie Island to retrieve a badly injured researcher and return him to Australia.

[75] In order to transfer the researcher to the ship, Hobart's personnel constructed a makeshift helipad, which was used by Thala Dan's helicopter to deliver the injured man to the destroyer.

[75] Hobart remained in Australian waters during the early 1980s, with the exception of deployments to Hawaii for RIMPAC, to the North West Indian Ocean for 6 months in 1981 and participation in Kangaroo exercises.

[4] In 1985, Hobart sailed to Canada to represent Australia at a naval review recognising the 75th anniversary of the Royal Canadian Navy's founding.

[4] During early 1988, the destroyer participated in activities celebrating Australia's Bicentenary, then later in the year sailed to join the RIMPAC exercise.

[4] In 1995, the ship was again deployed to South-east Asia, participated in celebrations of the 50th anniversary of the Pacific War's end, and visited New Zealand.

[77] Prior to the scuttling, preparatory work was done to ensure safe diving and minimal environmental impact, based on international best practices and mostly undertaken at Port Adelaide by contracted labour and some volunteers.

The goal was to maintain the vessel's character as a fighting ship, but in the interests of safety, some entrances were sealed, some doors, hatches and sharp and protruding objects were removed, and corridors and openings widened.

[78] The ship was sunk as a dive wreck on 5 November 2002 in Yankalilla Bay, South Australia at 35°28′51.6″S 138°09′26.0″E / 35.481000°S 138.157222°E / -35.481000; 138.157222, 4.8 nautical miles (8.9 km) west-north-west of Marina St. Vincent, within the Encounter Marine Park.