- Sydney Mason - Frank the garage man
- Larry J. Blake - Motorcycle cop
- Bert Stevens - Air Intelligence Command Officer
- Forbes Murray - Military Officer at Experiment
- Arthur Tovey - Officer/Civilian at Military Conference
- Alan Wells - Major Kimberly
- Nicky Blair - Military Officer at Experiment (uncredited)
- Jimmy Cross - Military Messenger (uncredited)
- Jack Deery - Military Officer (uncredited)
- Charles Evans - Dr. Alberts (uncredited)
- Raoul Freeman - Military Official (uncredited)
- Paul Frees - Alien (voice) (uncredited)
- James Gonzalez - Military Official (uncredited)
- Duke Green - Minor Role (uncredited)
- Ed Haskett - Military Official (uncredited)
- Clark Howat - Sgt. Nash (uncredited)
- Harry Lauter - Cutting - Generator Technician (uncredited)
- Don Marlowe - Minor Role (uncredited)
- William Meader - Worker in Control Tower (uncredited)
- Sol Murgi - Plane Passenger (uncredited)
- Forbes Murray - Military Officer at Experiment (uncredited)
- William J. O'Brien - Radio Listener (archive footage) (uncredited)
- Murray Pollack - Plane Passenger (uncredited)
- Mike Ragan - Tank Commander (uncredited)
- Alan Reynolds - Maj. Kimberly (uncredited)
- Dale Van Sickel - Man Crushed Beneath Wall (uncredited)
- Guy Way - Civilian Observing Saucer Attack (uncredited)
- Bob Whitney - Plane Passenger (uncredited)
- Frank Wilcox - Alfred Cassidy (uncredited)
- Beal Wong - Chinese Radio Listener (uncredited)
- William Woodson - Narrator (voice) (uncredited)
- Fred F. Sears
- Curt Siodmak
- Charles H. Schneer
- J.S. Westmoreland
Hugh Marlowe interpreta a Dr. Russell A. Marvin en la película.
Joan Taylor hace el papel de Carol Marvin.
Donald Curtis interpreta a Maj. Huglin en la película.
Morris Ankrum interpreta a Brig. Gen. John Hanley en la película.
Thomas Browne Henry interpreta a Vice Adm. Enright en la película.
Grandon Rhodes interpreta a Gen. Edmunds en la película.
John Zaremba interpreta a Prof. Kanter en la película.
Paul Frees interpreta a Alien (voice) en la película.
Frank Wilcox interpreta a Alfred Cassidy en la película.
Sydney Mason interpreta a Frank the garage man en la película.
Larry J. Blake hace el papel de Motorcycle cop.
Bert Stevens hace el papel de Air Intelligence Command Officer.
Forbes Murray interpreta a Military Officer at Experiment en la película.
Arthur Tovey interpreta a Officer/Civilian at Military Conference en la película.
Alan Wells interpreta a Major Kimberly en la película.
Nicky Blair hace el papel de Military Officer at Experiment (uncredited).
Jimmy Cross interpreta a Military Messenger (uncredited) en la película.
Jack Deery interpreta a Military Officer (uncredited) en la película.
Charles Evans interpreta a Dr. Alberts (uncredited) en la película.
Raoul Freeman interpreta a Military Official (uncredited) en la película.
Paul Frees interpreta a Alien (voice) (uncredited) en la película.
James Gonzalez interpreta a Military Official (uncredited) en la película.
Duke Green interpreta a Minor Role (uncredited) en la película.
Ed Haskett hace el papel de Military Official (uncredited).
Clark Howat interpreta a Sgt. Nash (uncredited) en la película.
Harry Lauter interpreta a Cutting - Generator Technician (uncredited) en la película.
Don Marlowe interpreta a Minor Role (uncredited) en la película.
William Meader interpreta a Worker in Control Tower (uncredited) en la película.
Sol Murgi interpreta a Plane Passenger (uncredited) en la película.
Forbes Murray interpreta a Military Officer at Experiment (uncredited) en la película.
William J. O'Brien interpreta a Radio Listener (archive footage) (uncredited) en la película.
Murray Pollack interpreta a Plane Passenger (uncredited) en la película.
Mike Ragan hace el papel de Tank Commander (uncredited).
Alan Reynolds hace el papel de Maj. Kimberly (uncredited).
Dale Van Sickel hace el papel de Man Crushed Beneath Wall (uncredited).
Guy Way interpreta a Civilian Observing Saucer Attack (uncredited) en la película.
Bob Whitney interpreta a Plane Passenger (uncredited) en la película.
Frank Wilcox hace el papel de Alfred Cassidy (uncredited).
Beal Wong interpreta a Chinese Radio Listener (uncredited) en la película.
William Woodson hace el papel de Narrator (voice) (uncredited).
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