Rod Steiger as Al Capone

Fay Spain as Maureen Flannery

James Gregory as Schaefler (narrator)

Martin Balsam as Mac Keeley, reporter

Nehemiah Persoff as Johnny Torrio

Murvyn Vye as George 'Bugs' Moran

Robert Gist as Dion O'Banion

Lewis Charles as Earl Weiss

Joe De Santis as Big Jim Colosimo

Sandy Kenyon as Bones Corelli

Raymond Bailey as Lawyer Brancato

Al Ruscio as Tony Genaro

Louis Quinn as Joe Lorenzo

Ron Soble as John Scalisi

Steve Gravers as Albert Anselmi

Raikin Ben-Ari as Ben Hoffman

Fred Aldrich as Funeral Spectator

Cindy Ames as Nurse

James Bacon as Reporter

Paul Bradley as Benefit Guest

Ralph Brooks as Convict in Yard at Alcatraz

Allen Jaffe as Bodyguard

Clegg Hoyt as Lefty

Paul Bryar as Police Inspector (uncredited)

Larry Chance as Vincent (uncredited)

Dick Cherney as Moran Associate (uncredited)

Mason Curry as Tailor (uncredited)

Russell Custer as Funeral Spectator (uncredited)

Rudy Doucette as Hood (uncredited)

Sol Gorss as Capone Hood at Polling Place (uncredited)

Mauritz Hugo as Hood (uncredited)

Forbes Murray as Pallbearer at Colosimo's Funeral (uncredited)

Dan Riss as Voice of Radio Announcer (uncredited)

Charles Sherlock as Reporter (uncredited)

Fred Sherman as Storekeeper (uncredited)