On 29 September 1965, "Harold J. Ellison" departed Norfolk with Destroyer Squadron (DesRon) 24 and headed via the Panama Canal for the Pacific Ocean. She served as plane guard for aircraft carriers on "Yankee Station" in the Tonkin Gulf, participated in "Sea Dragon" operations, patrolled on search and rescue duties and carried out naval gunfire support missions during the Vietnam War. Leaving Southeast Asia by steaming eastward through the Suez Canal, she completed her round-the-world cruise upon returning to Norfolk in April 1966. In July she entered the Norfolk Naval Shipyard for an overhaul which lasted for the rest of the year. After sea trials and refresher training early in 1967, "Harold J. Ellison" rejoined the United States Atlantic Fleet. She visited Brazil and crossed the equator on her way around Africa en route to the Middle East. During a port visit in Ethiopia, Emperor Haile Selassie was a guest aboard the ship. "Harold J. Ellison" also visited Kenya, Mauritius, Mozambique and Pakistan and returned in March 1971.