BUCHANAN joined the fleet under the command of Commander David A. Webster, and on completion of outfitting proceeded to her homeport, San Diego, California, to report for duty to Commander Cruiser-Destroyer Force, U. S. Pacific Fleet. On arrival in San Diego, BUCHANAN was ordered into a shakedown training period which included a cruise to Pearl Harbor, Hawaii. In Pearl Harbor, on 31 May 1962, she took part in the dedication ceremony of the USS ARIZONA Memorial, a memorial to the valiant men who gave their lives for their country on 7 December 1941. BUCHANAN returned to San Diego for completion of training, then pro-ceeded to Bremerton, Washington, for Post Shakedown Availability. November of 1962 found BUCHANAN returning to San Diego for unrestricted duty.

In April of 1963, BUCHANAN departed on her first WESTPAC deployment. During the eight-month absence from the United States, BUCHANAN received many compliments, especially in Melbourne, Australia, where she participated in the Coral Sea Festival's Twentieth Anniversary. In August 1963, Commander Webster was relieved by Commander Wilton A. Atkinson as the Commanding Officer. In December of 1963, BUCHANAN returned to San Diego for her first full regular overhaul and refresher training.

In January of 1965, she deployed for the second time to WESTPAC. In March 1965, Commander Atkinson was relieved as Commanding Officer by Commander Harrison C. Murray. During the second deployment BUCHANAN was awarded the Armed Forces Expeditionary Medal for service in the South China Sea in support of strike operations over hostile territory. In August 1965, BUCHANAN returned to San Diego and was dispatched to Long Beach Naval Shipyard for a three-month restricted availability. December 1965 found BUCHANAN participating in a missile testing project for the Navy.

From January to May 1966, BUCHANAN underwent type training including the First Fleet Exercise "GRAY GHOST." In June 1966, BUCHANAN began her third deployment to WESTPAC. In July, BUCHANAN became Flagship for Commander, SEVENTH FLEET during his official visit to Bangkok, Thailand. In this same month BUCHANAN's guns opened fire against hostile forces for the first time to conduct shore bombardment against concentrations of hostile troops in South Vietnam. In October 1966, Commander Murray was relieved by Commander William A. Spencer as Commanding Officer. In December of 1966, BUCHANAN returned to San Diego for leave and upkeep.

In March of 1967 she proceeded to Long Beach Naval Shipyard for a five-month regular overhaul. On completion of overhaul, BUCHANAN again underwent Ship's Qualification Trials and Refresher Training, then proceeded to Hunter's Point Naval Shipyard for shipboard alterations, at which time Commander Robert N. Congdon relieved Commander Spencer as Commanding Officer; then back to San Diego for the holidays.