- 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 hace el papel de Carol Marvin.
Donald Curtis interpreta a Maj. Huglin en la película.
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 interpreta a Prof. Kanter en la película.
Paul Frees interpreta a Alien (voice) en la película.
Frank Wilcox hace el papel de Alfred Cassidy.
Sydney Mason interpreta a Frank the garage man en la película.
Larry J. Blake interpreta a Motorcycle cop en la película.
Bert Stevens hace el papel de Air Intelligence Command Officer.
Forbes Murray hace el papel de Military Officer at Experiment.
Arthur Tovey hace el papel de Officer/Civilian at Military Conference.
Alan Wells interpreta a Major Kimberly en la película.
Nicky Blair interpreta a Military Officer at Experiment (uncredited) en la película.
Jimmy Cross hace el papel de Military Messenger (uncredited).
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 hace el papel de Military Official (uncredited).
Duke Green hace el papel de Minor Role (uncredited).
Ed Haskett interpreta a Military Official (uncredited) en la película.
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 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 hace el papel de Plane Passenger (uncredited).
Mike Ragan interpreta a Tank Commander (uncredited) en la película.
Alan Reynolds hace el papel de Maj. Kimberly (uncredited).
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 hace el papel de Plane Passenger (uncredited).
Frank Wilcox interpreta a Alfred Cassidy (uncredited) en la película.
Beal Wong hace el papel de Chinese Radio Listener (uncredited).
William Woodson interpreta a Narrator (voice) (uncredited) en la película.
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