Dr. Stuart Kelston/Narrator

Arthur Franz

Dr. Pat Blake

Helena Carter

David MacLean

Jimmy Hunt

Mr. George MacLean

Leif Erickson

Col. Fielding

Morris Ankrum

Mrs. Mary MacLean

Hillary Brooke

Army Sgt. Rinaldi

Max Wagner

Police Desk Sgt. Finlay (uncredited)

Walter Sande

Capt. Roth

Milburn Stone

Police Chief A.C. Barrows

Bert Freed

Kathy Wilson

Janine Perreau

Lt. Blair

Charles Gibb

Mr. Turner (uncredited)

John Eldredge

Officer Jackson

Douglas Kennedy

Dr. Bill Wilson (uncredited)

Robert Shayne

Officer Blaine

Charles Cane

Martian Intelligence (uncredited)

Luce Potter

Mutant Carrying David to 'Intelligence' (uncredited)

Lock Martin

Mrs. Wilson

Fay Baker

Mutant Carrying Dr. Blake to 'Intelligence' (uncredited)

Max Palmer

Sgt. Baker

Bill Phipps

Kelston's Secretary

Barbara Billingsley

MP

Richard Deacon

Mutant

Harry Monty

Major Clary

Gil Herman

Jim the Gas Station Attendant

Todd Karns

Pentagon Chief of Staff

Frank Wilcox

Col. Mayberry

William Forrest

Brainard (bit)

Peter Brocco