| Steve Buscemi | Enoch 'Nucky' Thompson |
| Kelly Macdonald | Margaret Thompson |
| Michael Shannon | Nelson Van Alden
(credit only) |
| Shea Whigham | Elias 'Eli' Thompson |
| Stephen Graham | Al Capone |
| Vincent Piazza | Lucky Luciano |
| Michael Kenneth Williams | Chalky White
(credit only) |
| Paul Sparks | Mickey Doyle
(credit only) |
| Jeffrey Wright | Valentin Narcisse |
| Ben Rosenfield | Willie Thompson
(credit only) |
| Gretchen Mol | Gillian Darmody |
| Anatol Yusef | Meyer Lansky |
| Ian Hart | Ethan Thompson |
| Domenick Lombardozzi | Ralph Capone |
| Marc Pickering | Deputy Sheriff Enoch Thompson |
| Matt Letscher | Joseph P. Kennedy |
| Maya Kazan | Mabel Jeffries-Thompson |
| John Ellison Conlee | Commodore Louis Kaestner |
| Michael Zegen | Benny Siegel |
| Travis Tope | Joe Harper |
| Louis Cancelmi | Mike D'Angelo |
| Erin Dilly | Eleanor Thompson |
| Nolan Lyons | Young Enoch Thompson |
| John C. Vennema | Lawrence Conors |
| Michael Countryman | Frank Wilson |
| Paul Fitzgerald | Charles Gabler |
| Richard Bekins | Theodore Rollins |
| Fred Arsenault | Agent #1 |
| Madelyn Barkocy | School Teacher |
| Greg Oliver Bodine | Agent #2 |
| Samantha Buck | Apartment Hunting Wife |
| Joseph Byrne | Agent #3 |
| Dustin Charles | Agent #4 |
| Sheffield Chastain | Luciano Bodyguard |
| Brian Myers Cooper | David |
| Destiny Monet Cruz | School Girl
(as Destiny Cruz) |
| Victoria Dennis | School Girl |
| Ryan Dinning | Young Eli Thompson |
| Amadeo Fusca | Joe Bonnano |
| Matt Harrington | Luciano Agent |
| Ethan Herschenfeld | Pinky Rabinowitz |
| Stephen Hill | Priest |
| Joseph Huffman | Boardwalk Walker |
| Vincent Ingrisano | Agent #5 |
| Salvatore Inzerillo | Thomas Gagliano |
| Rachel Kenney | Boardwalk Barker |
| Jack Koenig | Agent #6 |
| Bryonna Kristoferson | Queen Marinda |
| Katherine LaFountain | School Girl |
| Jordan Lage | King Neptune |
| Robert Langdon Lloyd | School Boy |
| Katence A. Lucas | School Girl |
| Regan Lutz | School Girl |
| Saint Marino | Kennedy Agent |
| Mary B. McCann | Matron
(as Mary McCann) |
| Christopher McLinden | Robert St. John |
| Scott Moreau | Agent
(as Scott Francis Moreau) |
| Isabelle Arely Palladino | Lady |
| Kevin Pariseau | Ma Capone |
| Madyson Pellegrino | School Girl |
| Salvatore Rossi | Sonny Capone |
| David Rossmer | Middle-Aged Agent |
| Alicia Ruggiero | Agent Men #1 |
| Thomas Schall | Middle-Aged Man |
| Jeffrey Schecter | |
| Michael Siberry | Wendell Lloyd |
| Brian Silliman | Photographer #1 |
| David Stam | |
| Shane Tunney | Princeton Student |
| John Virag | |
| Pernell Walker | |
| Danny Wolohan | |
| Christina Shea-Wright | (as Christina Wright) |
| Madeleine Yen | Young Gillian
(as Madeleine Rose Yen) |
| Jessica Swesey | Old Rumpus Dancer |
| Joseph K. Bevilacqua | David Sarnoff |
| Alexis Boursier | Chicago Reporter |
| Jared Brito | Irish Boy |
| Brett Joseph DePetrillo | Lucky Luciano Bodyguard |
| Rose Ftz | Vendor
(as Jennifer Suter) |
| Michael Wren Gucciardo | Brokers Client
(credit only) |
| Marcella Lentz-Pope | Mae Capone |
| Julia Losner | Neptune's Consort |
| Alexis Eileen Murphy | Boardwalk Girl
(as Alexis Murphy) |
| Jon Necaj | Boy at Al Capone's Trial |
| Jon Douglas Rainey | FBI Agent |
| Chris Skeries | Photographer |
| Joseph Anthony Sudol | Bootlegger |
| Roger Brenner | Waiter
(uncredited) |
| Phil Cappadora | Gangster
(uncredited) |
| David Chadwick | Red Levine
(uncredited) |
| Sarah Galvin | Mental Hospital Patient
(uncredited) |
| Christopher Gullo | Parade Dignitary
(uncredited) |
| Rich Petrillo | Luchiano Club Gun Check
(uncredited) |
| Jana Stella | Burlesque Waitress
(uncredited) |