| Steve Buscemi | Enoch 'Nucky' Thompson |
| Michael Pitt | James 'Jimmy' Darmody |
| Kelly Macdonald | Margaret Schroeder |
| Michael Shannon | Nelson Van Alden
(credit only) |
| Shea Whigham | Elias 'Eli' Thompson |
| Aleksa Palladino | Angela Darmody |
| Michael Stuhlbarg | Arnold Rothstein
(credit only) |
| 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 |
| Max Casella | Leo D'Alessio |
| Chris Mulkey | Boss Frank Hague |
| Geoff Pierson | Senator Walter Edge |
| Emily Meade | Pearl |
| Demosthenes Chrysan | George Anastos |
| Robert Clohessy | Alderman Jim Neary |
| Cat Davis | Commodore's Whore |
| Josie Gallina | Emily Schroeder |
| Lucy Gallina | Emily Schroeder |
| William Hill | Ward Boss O'Neill |
| Jimmie James | Klansman #1 |
| Anna Katarina | Isabelle Jeunet |
| Nikolas Kontomanolis | Chicago Patron |
| John Lantz | Tailor 1 |
| Al Linea | Matteo D'Allessio |
| Edward McGinty | Ward Boss Boyd |
| Erin McGrath | Edith Day |
| Declan McTigue | Teddy Schroeder |
| Rory McTigue | Teddy Schroeder |
| Tracy Middendorf | Babbette
(as Tracy Lynn Middendorf) |
| Derek Milhem | Attendant |
| Adam Mucci | Deputy Halloran |
| Connor Noon | Tommy Darmody |
| Brady Noon | Tommy Darmody |
| John Rue | Mayor Harry Bacharach |
| Frank Shattuck | Charlie Sheridan |
| Scott Sowers | Joseph Earl Dinler |
| Barbara Tirrell | Edith
(as Barbra Tirrell) |
| Susan Varon | Madam Regina |
| Victor Verhaeghe | Ward Boss Fleming |
| Sean Weil | Liam |
| Nathan Williams | Edge's Aide |
| Jeffrey C. Wolf | Babette's Dancer |
| Simone Assboeck | Babette's Dancer |
| Jennifer Bowles | Babette's Dancer |
| Tyler Ingram | Babette's Dancer |
| Mark Manley | Babette's Dancer |
| Dieter Riesle | Babette's Dancer |
| Frank Root | Babette's Dancer |
| Alison Solomon | Babette's Dancer |
| William Ward | Babette's Dancer |
| Meredith Riley Stewart | Babette's Dancer |
| Felicity Stiverson | Babette's Dancer |
| Jessica Swesey | Babette's Dancer |
| Marc Bicking | Councilman
(uncredited) |
| Robert Bizik | Brothel Customer
(uncredited) |
| Chris Cenatiempo | Bouncer
(uncredited) |
| Bill Geary | Party Guest
(uncredited) |
| Kimberly Huston | Partygoer
(uncredited) |
| Keith Leonard | Doorman
(uncredited) |
| Milton A. Marsh III | Babette's Busboy
(uncredited) |
| Orlando McDonald | Babette's Busboy
(uncredited) |
| Woodrow Morton | Busboy
(uncredited) |
| Lindsay Zehra Ozgunay | Brothel Worker
(uncredited) |
| Peter Riga | Coffee Drinker on Boardwalk
(uncredited) |