 William ShatnerAdmiral James T. Kirk | Admiral James T. Kirk |
 DeForest KelleyDr. Leonard 'Bones' McCoy | Dr. Leonard 'Bones' McCoy |
 James DoohanCaptain Montgomery 'Scotty' Scott | Captain Montgomery 'Scotty' Scott |
 George TakeiCmdr. Hikaru Sulu | Cmdr. Hikaru Sulu |
 Walter KoenigCmdr. Pavel Chekov | Cmdr. Pavel Chekov |
 Nichelle NicholsCmdr. Uhura | Cmdr. Uhura |
 Christopher LloydCmdr. Kruge | Cmdr. Kruge |
 Robin CurtisLt. Saavik | Lt. Saavik |
 Mark LenardAmbassador Sarek | Ambassador Sarek |
 Merritt ButrickDr. David Marcus | Dr. David Marcus |
 Judith AndersonVulcan High Priestess | Vulcan High Priestess |
 James B. SikkingCaptain Styles | Captain Styles |
 Phillip R. AllenCapt. Esteban | Capt. Esteban |
 Robert HooksAdmiral Morrow | Admiral Morrow |
 John LarroquetteMaltz | Maltz |
 Carl StevenSpock...Age 9 | Spock...Age 9 |
| VVadia PotenzaSpock...Age 13 | Spock...Age 13 |
 Stephen ManleySpock...Age 17 | Spock...Age 17 |
| JJoe W. DavisSpock at age 25 | Spock at age 25 |
 Leonard NimoyCaptain Spock / Elevator Voice | Captain Spock / Elevator Voice |
 Miguel FerrerFirst Officer | First Officer |
 Branscombe RichmondKlingon Gunner #2 | Klingon Gunner #2 |
 Frank WelkerSpock's Screams | Spock's Screams |
 Scott McGinnisStarfleet Cadet "Mr. Adventure" | Starfleet Cadet "Mr. Adventure" |
 Phil MorrisTrainee Foster | Trainee Foster |
 Jeanne MoriHelm Officer | Helm Officer |
 Grace Lee WhitneyCommander Janice Rand (Woman in Cafeteria) | Commander Janice Rand (Woman in Cafeteria) |
| NNanci RogersBar Waitress (uncredited) | Bar Waitress (uncredited) |
| PPaul SorensenCaptain | Captain |
 Danny RogersMerchantman First Officer (uncredited) | Merchantman First Officer (uncredited) |
