On 20 February 1968, "Mauna Kea" departed the Naval Weapons Station, Mare Island Annex, Vallejo, California for a WESTPAC deployment. "Mauna Kea" performed munitions underway replenishment (UNREP) operations to units of the 7th Fleet in the South China Sea and Gulf of Tonkin off the coast of South Vietnam. With the exception of UNREP operations at Subic Bay and a port visit to Hong Kong, "Mauna Kea" conducted these operations in direct support of combat operations from 14 March 1968 to 25 September 1968. During the period of 15 to 16 May 1968, "Mauna Kea" anchored at Anchorage #13 in Da Nang Harbor, with no disposition. On 17 May 1968, the USS "Mauna Kea" departed the Gulf of Tonkin en route to Subic Bay, arriving 18 May 1968. The ship visited Hong Kong during the period of 10 June to 15 June 1968. "Mauna Kea" departed Yankee Station on 26 September to return to her homeport, Concord, California, arriving on 14 October 1968.