Duffy of San Quentin

Louis Hayward

Edward 'Romeo' Harper

Joanne Dru

Anne Halsey

Paul Kelly

Warden Clinton T. Duffy

Maureen O'Sullivan

Gladys Duffy

George Macready

John C. Winant

Horace McMahon

Pierson

Irving Bacon

Doc Sorin

Joel Fluellen

Bill Lake

Joe Turkel

Frank Roberts

Jonathan Hale

Boyd

George Barrows

Convict

Marshall Bradford

Lowell

Peter Brocco

Nealy (uncredited)

George Bruggeman

Convict

James Conaty

Prison Board Member (uncredited)

Rudy Germane

Convict

Stuart Holmes

Judge

John Indrisano

Convict in Hospital Ward

Pete Kellett

Convict

DeForest Kelley

Eddie Lee