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

Robert Osterloh

Army Examining Doctor

Glenn Hardy

Radio Interviewer at Landing Site

Tyler McVey

Brady

House Peters Jr.

M.P. Captain at Barnhardt's

George Lynn

Conference Colonel Ryder

Dorothy Neumann

Margaret, Tom's secretary

Wheaton Chambers

Mr. Bleeker, jeweller

Carleton Young

Zone Five Lieutenant Colonel

Harry Harvey

The Cab Driver

Sammy Ogg

Sammy, boy witness

Bess Flowers

Lady Outside Jewelry Store

James Seay

Government Man

Grady Galloway

Radar Operator

Hassan Khayyam

Indian Newscaster

John Barton

British Newscaster

Stuart Whitman

Sentry (scene deleted)

Rama Bai

Scientific Delegate

John Burton

British Radio Announcer

Bill Welsh

Radio Announcer (voice)

Guy Williams

Radio Operator (uncredited)