TF 77, she shifted to "Operation Market Time", for trawler surveillance duty. Briefly detached twice in late June, she provided gunfire support in the I Corps area and destroyed several Viet Cong buildings and communications points. On 11 September, Southerland arrived back at San Diego. Nine months later, she was underway for another combat tour off Vietnam. On 8 July 1966, she arrived off the embattled coast and, for eleven days, operated with the carrier near the Mekong Delta. Detached on 19 July for fire support duty, she returned to the carrier on 28 July; and, at the end of the month, retired to Subic Bay. On 7 August, she was again off Vietnam. Until the end of the month, she operated in Tonkin Gulf with the aircraft carrier . ASW exercises followed; and, in mid-September, she sailed for Japan. At the end of October, she returned to Tonkin Gulf for search and rescue duty. On 23 November, Southerland completed her Vietnam tour and headed home. In February 1967, she served as ASW School Ship and, in March, as Engineering School Ship. From April to August, she underwent overhaul. In the fall, she conducted refresher training; and, on 28 December, she sailed for WestPac and another tour off Vietnam. From then until 28 June 1968 and again from 18 March to 3 July 1969, Southerland operated with the 7th Fleet on assignments similar to those in 1965 and 1966. In 1970, she sailed west in mid-June; operated in Japanese waters through the end of July; then steamed south, for Vietnam, on 6 August. There, she again alternated carrier escort and plane guard duties in Tonkin Gulf with fire support activities off the southern coast of the divided country until mid-November. On 1 December, she returned to San Diego. During the first half of 1971, Southerland spent two periods underway, one in January and one in April. Both were in conjunction with Composite Unit Training Exercises conducted in the southern California (SOCAL) operating area. On 29 June, she got underway from San Diego en route to the western Pacific. She remained in the Far East until 5 December, plane guarding for the carrier and visiting such oriental ports as Hong Kong, Singapore, and Subic Bay. After a 17-day passage, Southerland returned to San Diego on 22 December. Training ship, 1972–1980 On 2 June 1972, the ship entered the Long Beach Naval