Michael Rennie

Klaatu, alias Mr. Carpenter

Patricia Neal

Helen Benson

Billy Gray

Bobby Benson

Sam Jaffe

Prof. Jacob Barnhardt

Hugh Marlowe

Tom Stevens

Lock Martin

Gort

Freeman Lusk

General Cutler

Edith Evanson

Mrs. Crockett, landlady

Frank Conroy

Mr. Harley, Secretary to the President

Frances Bavier

Mrs. Barley, boarder

John Brown

George Barley, boarder

Olan Soule

Mr. Krull, boarder

Marjorie Crossland

Hilda, Barnhart's secretary

Elmer Davis

Elmer Davis

H.V. Kaltenborn

H. V. Kaltenborn

Drew Pearson

Drew Pearson

Gabriel Heatter

Gabriel Heatter (voice)

Harry Lauter

Lieutenant in Charge of Landing Site

James Doyle

Army Dr. White

Larry Dobkin

Balding Army Doctor