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