- 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 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 hace el papel de Gen. Edmunds.
John Zaremba hace el papel de Prof. Kanter.
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 interpreta a Military Officer at Experiment en la película.
Arthur Tovey interpreta a Officer/Civilian at Military Conference en la película.
Alan Wells hace el papel de Major Kimberly.
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 hace el papel de Dr. Alberts (uncredited).
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 interpreta a Minor Role (uncredited) en la película.
Ed Haskett interpreta a Military Official (uncredited) en la película.
Clark Howat hace el papel de Sgt. Nash (uncredited).
Harry Lauter hace el papel de Cutting - Generator Technician (uncredited).
Don Marlowe interpreta a Minor Role (uncredited) en la película.
William Meader interpreta a Worker in Control Tower (uncredited) en la película.
Sol Murgi hace el papel de Plane Passenger (uncredited).
Forbes Murray hace el papel de Military Officer at Experiment (uncredited).
William J. O'Brien hace el papel de Radio Listener (archive footage) (uncredited).
Murray Pollack interpreta a Plane Passenger (uncredited) en la película.
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 interpreta a Alfred Cassidy (uncredited) en la película.
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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