The summer of 1966 was spent in training and orienting midshipmen in the tactics and operations involved in the modern nuclear Navy. After a period of leave and upkeep in the fall, "Long Beach" sailed 7 November 1966 from Long Beach for the Far East. During this initial cruise, the ship served primarily as the Positive Identification Radar Advisory Zone (PIRAZ) unit in the northern Gulf of Tonkin. As such, her main responsibility was to "sanitize" returning US strike aircraft, ensuring that no enemy aircraft were attempting to evade identification by hiding amongst returning friendlies. Additionally, the ship provided support for an on-board Search and Rescue (SAR) helicopter unit. During this tour, "Long Beach" was responsible for directing the downing of one Soviet-made An-2 'Colt' aircraft that was attempting to engage South Vietnamese naval units. The shoot-down was executed by an F-4 Phantom II under the control of a "Long Beach" air intercept controller. The cruiser returned to Long Beach, California, in July 1967. In 1968, the ship was redeployed to the Gulf of Tonkin, shooting down a MiG 21 jet fighter near Vinh, with a RIM-8 Talos missile on 23 May 1968, at a range of . In June of the same year, she downed another MIG, this one at . She also directed other MIG kills by American fighters. She was the first ship to down an aircraft using SAMs in the Vietnam war and the incidents were not immediately publicized. "Long Beach" received a Navy Unit Commendation for the actions.