The main feature of the second half of "Sydney"s career was the twenty-five voyages the ship made to South Vietnam in support of the 1st Australian Task Force between May 1965 and November 1972. "Sydney", along with the civilian vessels and , was used to transport the majority of the Australian personnel and equipment contributed to the Vietnam War effort. These voyages earned "Sydney" the nickname "Vung Tau Ferry". The visits to Vietnam were interspersed by other duties, and "Sydney" continued to function as a training ship, with up to 30 midshipmen and 200 trainee sailors aboard at any given time.