Jason Robards as Al Capone

George Segal as Peter Gusenberg

Ralph Meeker as George Clarence 'Bugs' Moran

Jean Hale as Myrtle

Clint Ritchie as Jack McGurn

Frank Silvera as Nick Sorello

Joseph Campanella as Albert Wienshank

Richard Bakalyan as John Scalise

David Canary as Frank Gusenberg

Bruce Dern as Johnny May

Harold J. Stone as Frank Nitti

Kurt Kreuger as James Clark

Paul Richards as Charles Fischetti

Joe Turkel as Jake 'Greasy Thumb' Guzik

Milton Frome as Adam Heyer

Mickey Deems as Reinhold Schwimmer

John Agar as Dion O'Bannion

Celia Lovsky as Josephine Schwimmer

Tom Reese as Ted Newberry

Jan Merlin as Willie Marks

Alexander D'Arcy as Joe Aiello

Reed Hadley as Hymie Weiss

Gus Trikonis as Rio

Charles Dierkop as Salvanti

Tom Signorelli as Bobo Borotto

Rico Cattani as Albert Anselmi

Alex Rocco as Diamond

Leo Gordon as Heitler

Daniel Ades as Angelo Molina (uncredited)

Vincent Barbi as Witness (uncredited)

Laura Barry as Girl (uncredited)

Bob Brandon as Capone Board Member (uncredited)

Mushy Callahan as Hood (uncredited)

Mary Grace Canfield as Mrs. Doody, Landlady (uncredited)

Albert Cavens as Reporter (uncredited)

Bud Cokes as Hood (uncredited)

Russ Conway as Interrogator (uncredited)

Yutta D'Arcy as Gangster Girl (uncredited)

Tony Dante as Commuter (uncredited)

Jack Del Rio as Capone Board Member (uncredited)

George DeNormand as Clerk (uncredited)

Paul Frees as Narrator (voice) (uncredited)

Ron Gans as Chapman (uncredited)

James Gonzalez as Party Guest (uncredited)

Michele Guarini as Patsy Lolordo (uncredited)

Phil Harron as Capone Board Member (uncredited)

Jonathan Haze as Gangster Dressed as a Cop (uncredited)

Lisa Jak as Gangster Girl (uncredited)

Betsy Jones-Moreland as Poolside Interviewer (uncredited)

Richard Krisher as Desk Clerk (uncredited)

William Meader as Tenant (uncredited)

Mary Michael as Gangster Girl (uncredited)

Dick Miller as Gangster Dressed as a Cop (uncredited)

Ernesto Molinari as Capone Board Member (uncredited)

Barboura Morris as Jeanette Landsman (uncredited)

Jack Nicholson as Gino, Hit Man (uncredited)

Ron Nyman as Hood (uncredited)

Monty O'Grady as Party Guest (uncredited)

José Portugal as Mourner (uncredited)

Leoda Richards as Party Guest (uncredited)

Jerry Rush as Party Guest (uncredited)

Jeffrey Sayre as Party Guest (uncredited)

Ken Scott as Policeman (uncredited)

Bernard Sell as Hood (uncredited)

Sammy Shack as Vagrant (uncredited)

Joan Shawlee as Edna, Frank's Girlfriend (uncredited)

Buck Taylor as Poolside Interviewer 2 (uncredited)

Corinna Tsopei as Gangster Girl (uncredited)

Patrick Whyte as Judge at Party (uncredited)

Judith Woodbury as Party Guest (uncredited)