- Marianna Hill - Dr. Helen Noel
- Clint Howard - Balok
- Arlene Martel - T'Pring
- Keye Luke - Donald Cory
- Lee Meriwether - Losira
- Ricardo Montalban - Khan Noonien Singh
- Reggie Nalder - Shras
- John Colicos - Kor
- Julie Newmar - Eleen
- Jason Evers - Rael
- Perry Lopez - Lt. Esteban Rodriguez
- Roy Jenson - Cloud William
- Harry Basch - Brown
- Robert Brown - Lazarus
- Joan Collins - Edith Keeler
- Michael Ansara - Kang
- Jeff Corey - Plasus
- Lou Antonio - Lokai
- Arnold Moss - Anton Karidian
- Laurel Goodwin - Yeoman J. M. Colt (archive footage)
- Dyanne Thorne - First girl
- Marj Dusay - Kara
- Stanley Adams - Cyrano Jones
- William Marshall - Dr. Richard Daystrom
- Melvin Belli - Gorgan
- Jill Ireland - Leila Kalomi
- David Brian - John Gill
- Don Marshall - Boma
- Elisha Cook Jr. - Samuel Cogley
- Keith Andes - Akuta
- France Nuyen - Elaan
- Jason Wingreen - Dr. Linke
- Sid Haig - First Lawgiver
- Mariette Hartley - Zarabeth
- Angelique Pettyjohn - Shahna
- Leslie Parrish - Carolyn Palamas
- Kim Darby - Miri
- Julie Parrish - Miss Piper
- John Fiedler - Hengist
- Charles Maxwell - Virgil Earp
- Barry Atwater - Surak
- Brioni Farrell - Tula
- Madlyn Rhue - Marla McGivers
- Jane Wyatt - Amanda
- Sharon Acker - Odona
- Alfred Ryder - Professor Robert Crater
- Shirley Bonne - Ruth
- Charles Dierkop - Morla
- Michael J. Pollard - Jahn
- Robert Walker Jr. - Charlie Evans
- James Gregory - Dr. Tristan Adams
- Anthony Caruso - Bela Oxmyx
- Charles Drake - Commodore Stocker
- Rudy Solari - Salish
- Michael Dunn - Alexander
- David Frankham - Larry Marvick
- Louise Sorel - Rayna Kapec
- Fred Williamson - Anka
- Gary Lockwood - Lt. Cmdr. Gary Mitchell
- Sherry Jackson - Andrea
- BarBara Luna - Marlena Moreau
- Whit Bissell - Lurry
- Dick Durock - Elasian Guard #1
- Frank Overton - Elias Sandoval
- David Soul - Makora
- Johnny Haymer - The Constable
- Teri Garr - Roberta Lincoln
- Pamelyn Ferdin - Mary
- Theo Marcuse - Korob
- Jeffrey Hunter - Capt. Christopher Pike (archive footage)
- William Windom - Commodore William Decker
- Kathryn Hays - Gem
- John Abbott - Ayleborn
- Barbara Bouchet - Kelinda
- John Gabriel - Crewman (uncredited)
- John Crawford - Commissioner Ferris
- Michael Forest - Apollo
- David Opatoshu - Anan 7
- Elinor Donahue - Commissioner Nancy Hedford
- Nancy Kovack - Nona
- Jack Donner - Subcommander Tal
- Roger Perry - Captain John Christopher
- Logan Ramsey - Proconsul Claudius Marcus
- Richard Webb - Lt. Commander Benjamin Finney
- Roger C. Carmel - Harcourt Fenton Mudd
- Torin Thatcher - Marplon
- Peter Brocco - Claymare
- Georgia Schmidt - First Talosian (archive footage)
- Arthur Batanides - Lt. D'Amato
- Warren Stevens - Rojan
- Kathie Browne - Deela
- Harry Landers - Dr. Coleman
- Liam Sullivan - Parmen
- Richard Hale - Goro
- Percy Rodriguez - Commodore Stone
- Glenn Corbett - Zephram Cochran
- Lee Delano - Kalo
- Ed Peck - Col Fellini
- Frank Gorshin - Bele
- Steve Sandor - Lars
- Katherine Woodville - Natira
- Stephen Brooks - Ensign Garrovick
- James Daly - Flint
- Karen Steele - Eve McHuron
- Barbara Anderson - Lenore Karidian
- Lee Bergere - Abraham Lincoln
- Paul Fix - Dr. Piper
- Celia Lovsky - T'Pau
- Michael Dante - Maab
- William Smithers - Captain R.M. Merik
- Jeanne Bal - Nancy Crater
- Elizabeth Rogers - Lt. Palmer
- Elizabeth Rogers - The companion (voice)
- Michael Pataki - Korax
- Yvonne Craig - Marta
- Oliver McGowan - Caretaker
- Richard Compton - Washburn
- Bruce Hyde - Lt. Kevin Thomas Riley
- Lee Duncan - Evans
- Brian Tochi - Ray
- Charles Stewart - Captain Ramart
- Beverly Washburn - Arlene Galway
- Phillip Pine - Col. Green
- Michael Zaslow - Darnell
- Michael Zaslow - Jordan
- Peter Duryea - Lt. Tyler (archive footage)
- Valora Noland - Daras
- Paul Carr - Lt. Lee Kelso
- Mark Lenard - Sarek
- Mark Lenard - Romulan Commander
- Tige Andrews - Kras
- Gil Perkins - Master of Games
- Bruce Watson - Green
- David Hurst - Ambassador Hodin
- Antoinette Bower - Sylvia
- Susan Denberg - Magda
- Kenneth Washington - Watkins
- Steve Ihnat - Lord Garth of Izar
- Michael Witney - Tyree
- Kermit Murdock - The Prosecutor
- Robert Lansing - Gary Seven
- Michael Barrier - DeSalle
- Charles Napier - Adam
- John Winston - Lt. Kyle
- Billy Curtis - Small, copper skinned ambassador (uncredited)
- Joanne Linville - Romulan Commander
- Charlie Brill - Arne Darvin
- Don Keefer - Cromwell
- Celeste Yarnall - Yeoman Martha Landon
- Lloyd Haynes - Alden
- Carey Loftin - Truck driver (uncredited)
- Vic Tayback - Jojo Krako
- Ned Romero - Krell
- Dick Crockett - Andorian
- Gregg Palmer - Rancher (uncredited)
- Joan Marshall - Areel Shaw
- Grace Lee Whitney - Yeoman Janice Rand
- Bobby Bass - Guard (uncredited)
- Meg Wyllie - The Keeper (archive footage)
- Craig Huxley - Tommy Starnes
- Craig Huxley - Peter Kirk
- Ben Gage - Akaar
- Joseph Bernard - Tark
- William Schallert - Nilz Baris
- Maggie Thrett - Ruth
- Michael Strong - Corby
- Lawrence Montaigne - Decius
- Lawrence Montaigne - Stonn
- Jay Robinson - Lord Petri
- Bill Zuckert - Johnny Behan
- George Sawaya - Second Soldier
- Vince Howard - Crewman who stalks Uhura
- Andrea Dromm - Yeoman Smith
- Booker Bradshaw - Dr. M'Benga
- Jim Goodwin - Farrell
- Victor Lundin - Lieutenant
- Diana Muldaur - Dr. Miranda Jones
- Diana Muldaur - Ann Mulhall
- Rhodes Reason - Flavius Maximus
- Harry Townes - Reger
- Adam Roarke - C.P.O. Garrison (archive footage)
- Richard Derr - Admiral Fitzgerald
- Richard Derr - Barstow
- Leonard Mudie - Second survivor (uncredited)
- Ed Reimers - Admiral Fitzpatrick
- Joseph Ruskin - Galt
- Malachi Throne - The Keeper (voice) (uncredited)
- Victor Brandt - Watson
- Victor Brandt - Tongo Rad
- Sean Kenney - DePaul
- Sean Kenney - Crippled Capt. Christopher Pike
- John Hoyt - Dr. Phil Boyce (archive footage)
- Janos Prohaska - The Mugato
- Janos Prohaska - The Horta
- Janos Prohaska - Yarnek (uncredited)
- Sally Kellerman - Dr. Elizabeth Dehner
- Sheila Leighton - Luma
- Mary Linda Rapelye - Irina Galliulin
- Deborah Downey - Girl #1
- Skip Homeier - Dr. Sevrin
- Skip Homeier - Melakon
- Vic Perrin - Nomad (voice)
- Vic Perrin - Tharn
- Vic Perrin - Metron (voice)
- Richard Evans - Isak
- Patrick Horgan - Eneg
- William Campbell - Trelane
- William Campbell - Captain Koloth
- William Wintersole - Abrom
- Gilbert Green - S.S. Major
- Ed McCready - S.S. Trooper
- Diana Ewing - Droxine
- Davis Roberts - Dr. Ozaba
- Willard Sage - Thann
- Jan Shutan - Lt. Mira Romaine
- Tony Young - Kryton
- Byron Morrow - Admiral Westervliet
- Byron Morrow - Admiral Komack
- Charlene Polite - Vanna
- Anthony D. Call - Dave Bailey
- Phyllis Douglas - Yeoman Mears
- Phyllis Douglas - Girl #2 (Mavig)
- MaKee K. Blaisdell - Spinelli
- MaKee K. Blaisdell - Singh
- John Megna - The Bonk Bonk on the Head Boy
- Ted Cassidy - Balok's puppet (voice)
- Ted Cassidy - Ruk
- Ted Cassidy - Gorn (voice)
- Lev Mailer - S.S. Lieutenant
- Lev Mailer - Bilar
- Morgan Woodward - Captain Tracy
- Morgan Woodward - Dr. Simon van Gelder
- Bob Johnson - First Talosian (voice) (uncredited)
- Bob Johnson - Starbase 6 commander (voice)
- Morgan Farley - Yang Scholar
- Morgan Farley - Hacom
- Barbara Babcock - Philana
- Barbara Babcock - Trelane's mother (voice)
- Barbara Babcock - Mea 3
- Barbara Babcock - Commander Loskene (voice)
- Barbara Babcock - Lights of Zetar (voice)
- Barbara Babcock - Beta Five Computer (voice) / Isis (voice)
- Paul Comi - Stiles
- John Warburton - The Centurion
- Emily Banks - Tonia Barrows
- Richard Carlyle - Jaeger
- James Farley - Lang
- Grant Woods - Kelowitz
- Hal Lynch - Air Police Sergeant
- Charles Macaulay - Landru
- Charles Macaulay - Jaris
- Gene Lyons - Ambassador Fox
- Miko Mayama - Yeoman Tamula
- Abraham Sofaer - Melkotian (voice)
- Abraham Sofaer - Thasian (voice)
- Ken Lynch - Chief Engineer Vanderberg
- Brad Weston - Ed Appel
- Biff Elliot - Schmitter
- Stewart Moss - Joe Tormolen
- Stewart Moss - Hanar
- Janet MacLachlan - Charlene Masters
- Jon Lormer - Tamar
- Jon Lormer - Old Man
- Hal Baylor - Policeman
- Walker Edmiston - Balok (voice) (uncredited)
- Walker Edmiston - Provider #2
- Walker Edmiston - Space Central (voice)(uncredited)
- Walker Edmiston - Transporter Chief (voice) (uncredited)
- Walker Edmiston - Warning call from the S.S. Deidre (voice)
- Joan Swift - Aurelan Kirk
- Maurishka - Yeoman Zahra
- Majel Barrett - Nurse Christine Chapel
- Majel Barrett - Nurse Christine Chapel / Enterprise Computer (voice)
- Majel Barrett - Nurse Chapel
- Majel Barrett - Number One
- Majel Barrett - Number One (archive footage)
- Gene Dynarski - Krodak
- Gene Dynarski - Ben Childress
- Richard Tatro - Norman
- John Harmon - Bum who finds phaser
- John Harmon - Tepo
- Alyce Andrece - Alice #1 -#250
- William O'Connell - Thelev
- John Wheeler - Gav
- Barry Russo - Lt. Commander Giotto
- Barry Russo - Commodore Wesley
- Sarah Marshall - Janet Wallace
- Pilar Seurat - Sybo
- Jane Ross - Tamoon
- Mickey Morton - Kloog
- Bruce Mars - Crewman
- Bruce Mars - Finnegan
- Ron Soble - Wyatt Earp
- Rex Holman - Morgan Earp
- Bonnie Beecher - Sylvia
- Lezlie Dalton - Drea
- Alani iLongwe - Lt. Shea
- Julie Cobb - Yeoman Thompson
- Garth Pillsbury - Wilson
- Garth Pillsbury - Troglyte prisoner
- Lloyd Kino - Wu
- Sabrina Scharf - Miramanee
- Barbara Baldavin - Angela Teller
- Barbara Baldavin - Angela Martine
- Barbara Baldavin - Communications Officer
- Rees Vaughn - Latimer
- Alice Rawlings - Jame Finney
- Ian Wolfe - Septimus
- Ian Wolfe - Atoz
- Karl Held - Lindstrom
- Geoffrey Binney - Compton
- Jon Kowal - Herm Gossett
- Vince Deadrick Sr. - Mathews
- Budd Albright - Rayburn
- Hagan Beggs - Lt. Hansen
- William Sargent - Dr. Thomas Leighton
- Francine Pyne - Nancy III
- David L. Ross - Galloway
- David L. Ross - Johnson
- Bart La Rue - Yarnek (voice)
- Bart La Rue - Provider #1
- Ron Veto - Harrison
- Ron Veto - Harrison / Organian Villager
- Ron Veto - Eminiar Guard
- Sean Morgan - Crewman
- Robert Sampson - Sar 6
- Tanya Lemani George - Kara
- April Tatro - Isis - human form
- Jerry Ayres - Rizzo / O'Herlihy
- Irene Kelly - Sirah
- Sheldon Collins - Tough Kid
- Bobby Clark - Gorn (stunts)
- Susan Howard - Mara
- Bill Blackburn - Lieutenant Hadley (voice)
- Virginia Aldridge - Lt. Karen Tracy
- Judith McConnell - Yeoman Tankris (as Judy McConnell)
- Carolyn Nelson - Yeoman Atkins
- Suzanne Lodge - Argelian Waitress (uncredited)
- Felix Locher - Mr. Johnson
- Laura Wood - Mrs. Johnson
- Bob Herron - Kahless
- Anthony Larry Paul - Lt. Berkley (uncredited)
- Sandra Smith - Dr. Janice Lester
- Walter Soo Hoo - Crewman (uncredited)
- James X. Mitchell - Lt. Josephs
- Erik Holland - Ekor
- Alan Bergmann - Lal
- Robert Fortier - Tomar
- Shari Nims - Sayana
- James Drake - Sick-Bay Intern (uncredited)
- James Drake - Security Guard (uncredited)
- Gene Roddenberry - Enterprise Chef (voice) (uncredited)
- Rhae Andrece - Alice #251-#500
- Kay Elliot - Stella Mudd
- Patricia McNulty - Yeoman Tina Lawton
- Sam Gilman - Doc Holliday
- Charles Seel - Ed
- Guy Raymond - Trader
- John Meredyth Lucas
- Edward K. Milkis
- Byron Haskin
- John D. F. Black
- Fred Freiberger
- Robert H. Justman
Ricardo Montalban interpreta a Khan Noonien Singh en la serie.
Elisha Cook Jr. interpreta a Samuel Cogley en la serie.
Mark Lenard hace el papel de Romulan Commander.
Frank Gorshin interpreta a Bele en la serie.
Ken Lynch interpreta a Chief Engineer Vanderberg en la serie.
Stanley Adams hace el papel de Cyrano Jones.
Elinor Donahue interpreta a Commissioner Nancy Hedford en la serie.
Majel Barrett interpreta a Nurse Chapel en la serie.
Ian Wolfe hace el papel de Atoz.
Jane Wyatt interpreta a Amanda en la serie.
Capítulo disponible en las siguientes plataformas:
