Richard Eyer as Timmie Merrinoe

Philip Abbott as Dr. Tom Merrinoe

Diane Brewster as Mary Merrinoe

Harold J. Stone as Gen. Swayne

Robert H. Harris as Prof. Frank Allerton

Dennis McCarthy as Col. Macklin

Alexander Lockwood as Arthur Kelvaney

John O'Malley as Prof. Baine

Gage Clarke as Dr. Bannerman

Than Wyenn as Prof. Zeller

Jefferson Dudley Searles as Prof. Foster

Alfred Linder as Martin / Computer

Ralph Votrian as 1st Gate Sergeant

Michael Miller as 2nd Gate Sergeant

Rayford Barnes as Capt. McLaren (uncredited)

Helen Kleeb as Miss Vandergrift (uncredited)

Alvy Moore as Scientist (uncredited)

Gary Vinson as Young soldier (uncredited)

Marvin Miller as Robby the Robot (voice) (uncredited)