Jeffrey Hunter

Christopher Pike

Leonard Nimoy

Spock

Majel Barrett

Number One

Susan Oliver

Vina

Meg Wyllie

The Keeper

Peter Duryea

Lieutenant José Tyler

Laurel Goodwin

Yeoman J. M. Colt

Clegg Hoyt

Transporter Chief Pitcairn

Malachi Throne

The Keeper (voice)

Michael Dugan

The Kaylar

Georgia Schmidt

First Talosian

Robert C. Johnson

First Talosian (voice)

Serena Sande

Second Talosian

Jon Lormer

Dr. Theodore Haskins

Adam Roarke

C.P.O. Garrison

Leonard Mudie

Second Survivor

Anthony Jochim

Third Survivor

Edward Madden

Enterprise Geologist

Robert Phillips

Orion Space Officer

Joseph Mell

Earth Trader

Janos Prohaska

Anthropoid Ape / Humanoid Bird

Carol Daniels

Bridge Crewmember (uncredited)