Following trials from October 1964 to May 1965, the new guided missile destroyer conducted shakedown off the west coast into July, before she participated in anti-aircraft and electronic warfare Exercise "Hot Stove" from 26 August to 3 September.

While en route on 31 October, the American task group received a radio message reporting that Japanese merchantman Tokei Maru had suffered an explosion on board.

After providing medical assistance which saved the man's life and having left Tokei Maru a supply of medicine to suffice until the Japanese ship could make port, Waddell rejoined her consorts.

Only one day after reaching Subic Bay, Waddell got underway on 2 November for the coast of Vietnam and her first deployment to "Yankee Station" W-5, in the Tonkin Gulf.

During her second WestPac deployment in Vietnamese waters, the destroyer fired some 2,000 rounds of ammunition while winning the reputation of being "the busiest ship in the Tonkin Gulf" before heading home.

She entered the Long Beach Naval Shipyard on 4 August and commenced an extensive overhaul which lasted through the end of the year 1967 and into February 1968.

She returned to WestPac that summer—with logistics stops at Pearl Harbor and Midway en route—and arrived at her new home port of Yokosuka, Japan, on 1 August 1968.

After a quick trip via Buckner Bay to Yokosuka, Waddell sped back to the "gun line" in late February and resumed her gunfire support duties on 1 March.

During the first week of April, the downing by North Koreans of a Navy EC-121 Connie early-warning intelligence aircraft in the Sea of Japan greatly increased tension in the Far East.

Waddell departed the "gun line" at 22 knots, refueled at Buckner Bay, and arrived in the Strait of Tsushima to screen aircraft carriers Ticonderoga and Ranger.

Returning to the "gun line," Waddell then lobbed shells at Viet Cong (VC) camps and infiltration points from waters off Phu Quoc Island in the Gulf of Siam in support of Operation "Javelin," before she was assigned to the Mekong Delta region.

Waddell was decommissioned and stricken from the Naval Vessel Register on 1 October 1992, sold to Greece and renamed Nearchos after the ancient Cretan admiral Nearchus.