Walter Pidgeon

as Admiral Harriman Nelson

Robert Sterling

as Captain Lee Crane

Barbara Eden

as Lieutenant Cathy Conners

Peter Lorre

as Comm. Lucius Emery

Joan Fontaine

as Dr. Susan Hiller

Michael Ansara

as Dr. Miguel Alvares

Frankie Avalon

as Lieutenant Chip Romano

Regis Toomey

as Dr. Jamieson

John Litel

as Vice Admiral B.J. Crawford

Howard McNear

as Congressman Llewellyn Parker

Henry Daniell

as Dr. Zucco

Robert Easton

as Sparks

Charles Tannen

as CPO Mack Gleason

Mark Slade

as Seaman Jimmy 'Red' Smith

Del Monroe

as Seaman Kowski

Jonathan Gilmore

as Seaman George Young

Anthony Monaco

as Cookie

Skip Ward

as Crew Member

Michael Ford

as Crew Member

William Herrin

as Crew Member (Uncredited)

Robert Buckingham

as Crew Member (Uncredited)

Richard Adams

as Crew Member (Uncredited)

Jimmy Murphy

as Crew Member (Uncredited)

George Diestel

as Lieutenant Hodges (Uncredited)

Larry Gray

as Dr. Newmar (Uncredited)

David McLean

as Ned Thompson (Uncredited)

Edward Rickard

as Officer (Uncredited)

Charles Dierkop

as Seaview Pilot (Uncredited)

Kendrick Huxham

as UN Committee Chairman (Uncredited)

Art Baker

as UN Commentator (Uncredited)

Rodger Terry

as Guard (Uncredited)

Brad Brown

as Guard (Uncredited)

Raoul Freeman

as Delegate (Uncredited)

Al Bain

as Delegate (Uncredited)

Harry Baum

as Delegate (Uncredited)

Benjie Bancroft

as Delegate (Uncredited)

Michael Cirillo

as Delegate (Uncredited)

Harry Denny

as Delegate (Uncredited)

John Giovanni

as Delegate (Uncredited)

Bhupesh Guha

as Delegate (Uncredited)

Esther Ying Lee

as Delegate (Uncredited)

Robert Locke Lorraine

as Delegate (Uncredited)

George Nardelli

as Delegate (Uncredited)

Paul Power

as Delegate (Uncredited)

Paul Ravel

as Delegate (Uncredited)

Scott Seaton

as Delegate (Uncredited)

Leslie Sketchley

as Delegate (Uncredited)

Ray Spiker

as Delegate (Uncredited)

Hal Taggart

as Delegate (Uncredited)

Robert Strong

as Delegate (Uncredited)

Ron Nyman

as Crew Member (uncredited)