| Steve Buscemi | Enoch 'Nucky' Thompson |
| Kelly Macdonald | Margaret Thompson |
| Michael Shannon | Nelson Van Alden |
| Shea Whigham | Elias 'Eli' Thompson |
| Michael Stuhlbarg | Arnold Rothstein |
| Stephen Graham | Al Capone |
| Vincent Piazza | Lucky Luciano |
| Michael Kenneth Williams | Chalky White |
| Anthony Laciura | Eddie Kessler |
| Paul Sparks | Mickey Doyle |
| Jack Huston | Richard Harrow |
| Charlie Cox | Owen Sleater |
| Bobby Cannavale | Gyp Rosetti |
| Gretchen Mol | Gillian Darmody |
| James Cromwell | Andrew W. Mellon |
| Stephen Root | Gaston Means - Special Investigator |
| Dominic Chianese | Leander Cephas Whitlock |
| Geoff Pierson | Senator Walter Edge |
| Anatol Yusef | Meyer Lansky |
| Stephen DeRosa | Eddie Cantor |
| Meg Steedle | Lillian 'Billie' Kent |
| Erik LaRay Harvey | Dunn Purnsley |
| Patrick Kennedy | Dr. Douglas Mason |
| Arron Shiver | Dean O'Banion |
| Katy Wright-Mead | Roberta - Diner Waitress |
| Kathryn Barnhardt | Student 2 |
| Daniel Martin Berkey | Senator 1 |
| P.J. Brown | Prohibition Agent Emmet L. Coughlin |
| Chris Caldovino | Tonino Sandrelli |
| Emily Dorsch | Cornelia Predock |
| John Harrington Bland | Scotty Gulliver - Faraday Irons Manager |
| Michael Hayward-Jones | Senator 2 |
| Matt Hobby | Thompson House Servant Phillip |
| Mike Houston | Ralph - Faraday Irons Salesman |
| Ed Jewett | Jess Smith - Daugherty's Aide |
| Anna Katarina | Madame Isabelle Jeunet |
| Megan Loya McQueen | Prostitute 1 |
| Kate Loprest | Student Corrine |
| Rebecca Luker | Sister Agnes |
| Daniel Marconi | Paper Boy |
| Melissa McMeekin | Nurse |
| Oona Mekas | Helen Russell - Dr. Mason's Fiancee |
| Tracy Middendorf | Babette |
| Matthew F. O'Connor | Boardwalk Barker |
| Ted Pejovich | Senator 3 |
| Jen Ponton | Student 1 |
| Richard James Porter | Impatient Man |
| Johnny Pruitt | Vern - Choreographer |
| Noah Racey | Dancer |
| Christiane Seidel | Sigrid Mueller |
| Clayton Dean Smith | Employee |
| Eric Stretch | Sterling |
| Nathan Williams | Harvey - Informer |
| Michael Zegen | Benny Siegel |
| Anne Bergstedt | Gillian's Prostitute |
| John Buscemi | Bodyguard |
| Joseph Dimartino | Four Deuces Bartender |
| David Itchkawitz | Upscale Citizen |
| Paul Jude Letersky | Farraday Iron Salesman |
| Heather Lind | Katy |
| Jena Mroz | Gillian's Prostiute |