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

Harry Lauter

Lieutenant in Charge of Landing Site

Robert Osterloh

Army Examining Doctor

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

Bess Flowers

Lady Outside Jewelry Store

James Seay

Government Man (uncredited)

Stuart Whitman

Sentry (scene deleted)

Guy Williams

Radio Operator (uncredited)