Marshall Thompson as Major Jeff Cummings

Kynaston Reeves as Prof. R. E. Walgate

Kim Parker as Barbara Griselle

Stanley Maxted as Col. Butler

Terry Kilburn as Capt. Al Chester

James Dyrenforth as Mayor Hawkins

Robert MacKenzie as Const. Howard Gibbons

Peter Madden as Dr. Bradley

Gil Winfield as Dr. Warren

Michael Balfour as Sgt. Kasper

Launce Maraschal as Melville

Meadows White as Ben Adams

E. Kerrigan Prescott as Atomic Engineer

Lala Lloyd as Amelia Adams

Shane Cordell as Nurse

Sheldon Allan as Sentry (uncredited)

Alexander Archdale as Minister (uncredited)

Eddie Boyce as Jacques Griselle (uncredited)

Victor Hagan as Villager (uncredited)

Victor Harrington as Villager (uncredited)

Jack Hetherington as Sergeant in Office (uncredited)

Richard Neller as Townsman (uncredited)

Tom Watson as Technical Sergeant (uncredited)