Michael Rennie
Role: Klaatu, alias Mr. Carpenter
Patricia Neal
Role: Helen Benson
Billy Gray
Role: Bobby Benson
Sam Jaffe
Role: Prof. Jacob Barnhardt
Hugh Marlowe
Role: Tom Stevens
Freeman Lusk
Role: General Cutler
Edith Evanson
Role: Mrs. Crockett, landlady
Frank Conroy
Role: Mr. Harley, Secretary to the President
Frances Bavier
Role: Mrs. Barley, boarder
John Brown
Role: George Barley, boarder
Olan Soule
Role: Mr. Krull, boarder
Marjorie Crossland
Role: Hilda, Barnhart's secretary
Elmer Davis
Role: Elmer Davis
H.V. Kaltenborn
Role: H. V. Kaltenborn
Drew Pearson
Role: Drew Pearson
Gabriel Heatter
Role: Gabriel Heatter (voice)
Harry Lauter
Role: Lieutenant in Charge of Landing Site
James Doyle
Role: Army Dr. White
Larry Dobkin
Role: Balding Army Doctor
Robert Osterloh
Role: Army Examining Doctor
Glenn Hardy
Role: Radio Interviewer at Landing Site
House Peters Jr.
Role: M.P. Captain at Barnhardt's
George Lynn
Role: Conference Colonel Ryder
Dorothy Neumann
Role: Margaret, Tom's secretary
Wheaton Chambers
Role: Mr. Bleeker, jeweller
Carleton Young
Role: Zone Five Lieutenant Colonel
Harry Harvey
Role: The Cab Driver
Sammy Ogg
Role: Sammy, boy witness
Bess Flowers
Role: Lady Outside Jewelry Store
James Seay
Role: Government Man
Grady Galloway
Role: Radar Operator
Hassan Khayyam
Role: Indian Newscaster
John Barton
Role: British Newscaster
Stuart Whitman
Role: Sentry (scene deleted)
Rama Bai
Role: Scientific Delegate
John Burton
Role: British Radio Announcer
Bill Welsh
Role: Radio Announcer (voice)
