William Shatner as Admiral James T. Kirk

DeForest Kelley as Dr. Leonard 'Bones' McCoy

James Doohan as Captain Montgomery 'Scotty' Scott

George Takei as Cmdr. Hikaru Sulu

Walter Koenig as Cmdr. Pavel Chekov

Nichelle Nichols as Cmdr. Uhura

Christopher Lloyd as Cmdr. Kruge

Robin Curtis as Lt. Saavik

Mark Lenard as Ambassador Sarek

Merritt Butrick as Dr. David Marcus

Judith Anderson as Vulcan High Priestess

James B. Sikking as Captain Styles

Phillip R. Allen as Capt. Esteban

Robert Hooks as Admiral Morrow

John Larroquette as Maltz

Carl Steven as Spock...Age 9

Vadia Potenza as Spock...Age 13

Stephen Manley as Spock...Age 17

Joe W. Davis as Spock at age 25

Leonard Nimoy as Captain Spock / Elevator Voice

Miguel Ferrer as First Officer

Branscombe Richmond as Klingon Gunner #2

Frank Welker as Spock's Screams

Scott McGinnis as Starfleet Cadet "Mr. Adventure"

Phil Morris as Trainee Foster

Jeanne Mori as Helm Officer

Grace Lee Whitney as Commander Janice Rand (Woman in Cafeteria)

Nanci Rogers as Bar Waitress (uncredited)

Paul Sorensen as Captain

Danny Rogers as Merchantman First Officer (uncredited)