David Graham

Dr. Horatio Beaker / Mitch the Monkey / Morse Operator (voice)

Sylvia Anderson

Jimmy Gibson (voice) (uncredited)

Paul Maxwell

Colonel Steve Zodiac (voice)

Gerry Anderson

Robert the Robot (voice) (uncredited)

John Bluthal

Commander Wilbur Zero / Jock Campbell (voice)

Graydon Gould

Mike Mercury / Jason Munroe III (voice)

George Murcell

Professor Rudolph Popkiss (voice) (credit only)

Nicholas Parsons

Sheriff Tex Tucker / Telegraph Operator Dan Morse (voice)

Kenneth Connor

Dusty the Dog / Rocky the Horse / Foreman (voice)

Denise Bryer

Martha 'Ma' Jones (voice)