| Steve Buscemi | Enoch 'Nucky' Thompson |
| Michael Pitt | James 'Jimmy' Darmody |
| Kelly Macdonald | Margaret Schroeder |
| Michael Shannon | Nelson Van Alden |
| Shea Whigham | Elias 'Eli' Thompson |
| Aleksa Palladino | Angela Darmody |
| Michael Stuhlbarg | Arnold Rothstein |
| Stephen Graham | Al Capone |
| Vincent Piazza | Lucky Luciano |
| Paz de la Huerta | Lucy Danziger |
| Michael Kenneth Williams | Chalky White |
| Anthony Laciura | Eddie Kessler |
| Paul Sparks | Mickey Doyle |
| Dabney Coleman | Commodore Louis Kaestner |
| Gretchen Mol | Gillian Darmody |
| Greg Antonacci | Johnny Torrio |
| Edoardo Ballerini | Ignatius D'Alessio |
| Dana Ivey | Mrs. McGarry |
| Peter McRobbie | Supervisor Elliot |
| Chris Mulkey | Boss Frank Hague |
| Erik Weiner | Agent Sebso |
| Bambi | Upscale Whore #2 |
| Johann Carlo | Teresina Capone |
| Chris Cenatiempo | Bouncer |
| Peter Claymore | Grey-Haired Man |
| Darlinda Just Darlinda | Upscale Whore #1 |
| Lucy Gallina | Emily Schroeder |
| Josie Gallina | Emily Schroeder |
| Enid Graham | Rose Van Alden |
| William Hill | Ward Boss O'Neill |
| Anna Katarina | Isabelle Jeunet |
| Marcella Lentz-Pope | Mae Capone |
| Nicholas Alexander Martino | Pius D'Alessio |
| Declan McTigue | Teddy Schroeder |
| Rory McTigue | Teddy Schroeder |
| Mick O'Rourke | Thug #2 |
| Faith Sandberg | Kitty |
| Kylie Sanders | Ruby |
| Jodie Sanders | Ruby |
| Lauren Sharpe | Ukulele Girl |
| Frank Shattuck | Charlie Sheridan |
| Barbara Tirrell | Edith |
| Maranda Barskey | Singing Whore |
| Whitney Bashor | Coat Check Girl |
| Alex Eckstein | Sonny |
| Ben Eckstein | Sonny |
| Caleb Eckstein | Sonny |
| Mat Hostetler | Fed #1 |
| Mattilyn Rochester Kravitz | Clara Chariton |
| Maggie Lakis | Singing Whore |
| Kevin Nagle | Thug #1 |
| Megan Reinking | Annabelle |
| Robert Bizik | Brothel Customer |
| Graig Guggenheim | Torio Thug |
| Nicky Julius | Gino |
| Brady Noon | Tommy Darmody |
| Connor Noon | Tommy Darmody |
| Lindsay Zehra Ozgunay | Al Capone's Brothel Worker |
| Kent Sladyk | Gangster |
| Sarah Sugrue | Young Girl |
| Dolores Winn | Still Worker |