- 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)
- 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)
- Dale Van Sickel - Man Crushed Beneath Wall (uncredited)
- Guy Way - Civilian Observing Saucer Attack (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 interpreta a Carol Marvin en la película.
Donald Curtis hace el papel de Maj. Huglin.
Morris Ankrum hace el papel de Brig. Gen. John Hanley.
Thomas Browne Henry interpreta a Vice Adm. Enright en la película.
Grandon Rhodes interpreta a Gen. Edmunds en la película.
John Zaremba hace el papel de Prof. Kanter.
Paul Frees interpreta a Alien (voice) en la película.
Frank Wilcox interpreta a Alfred Cassidy en la película.
Sydney Mason hace el papel de Frank the garage man.
Larry J. Blake interpreta a Motorcycle cop en la película.
Bert Stevens interpreta a Air Intelligence Command Officer en la película.
Forbes Murray hace el papel de Military Officer at Experiment.
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 hace el papel de Military Messenger (uncredited).
Jack Deery interpreta a Military Officer (uncredited) en la película.
Charles Evans hace el papel de Dr. Alberts (uncredited).
Raoul Freeman hace el papel de Military Official (uncredited).
Paul Frees interpreta a Alien (voice) (uncredited) en la película.
James Gonzalez interpreta a Military Official (uncredited) en la película.
Duke Green hace el papel de Minor Role (uncredited).
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 hace el papel de Worker in Control Tower (uncredited).
Sol Murgi interpreta a Plane Passenger (uncredited) en la película.
Forbes Murray hace el papel de Military Officer at Experiment (uncredited).
William J. O'Brien interpreta a Radio Listener (archive footage) (uncredited) en la película.
Murray Pollack hace el papel de Plane Passenger (uncredited).
Mike Ragan interpreta a Tank Commander (uncredited) en la película.
Alan Reynolds interpreta a Maj. Kimberly (uncredited) en la película.
Dale Van Sickel interpreta a Man Crushed Beneath Wall (uncredited) en la película.
Guy Way hace el papel de Civilian Observing Saucer Attack (uncredited).
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 interpreta a Narrator (voice) (uncredited) en la película.
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