| Steve Buscemi | Enoch 'Nucky' Thompson |
| Kelly Macdonald | Margaret Thompson
(credit only) |
| Michael Shannon | Nelson Van Alden |
| Shea Whigham | Elias 'Eli' Thompson |
| Michael Stuhlbarg | Arnold Rothstein |
| Stephen Graham | Al Capone |
| Vincent Piazza | Lucky Luciano
(credit only) |
| Michael Kenneth Williams | Chalky White |
| Anthony Laciura | Eddie Kessler
(credit only) |
| Paul Sparks | Mickey Doyle
(credit only) |
| Jack Huston | Richard Harrow |
| Ron Livingston | Roy Phillips |
| Jeffrey Wright | Valentin Narcisse |
| Gretchen Mol | Gillian Darmody |
| Patricia Arquette | Sally Wheet |
| Domenick Lombardozzi | Ralph Capone |
| Wrenn Schmidt | Julia Sagorsky |
| Arron Shiver | Dean O'Banion |
| Fredric Lehne | Owney Madden |
| Ty Robinson | Samuel Crawford
(as Ty Michael Robinson) |
| Margot Bingham | Daughter Maitland |
| Mark Borkowski | Paul Sagorsky |
| Surya Botofasina | Mr. Coates |
| Joseph Anthony Byrd | Sterling |
| David Campbell | Tom (Nucky's Bodyguard) |
| Peter Claymore | Grey-Haired Man |
| Rick Crom | Sagorsky's Attorney |
| Justiin A. Davis | Lester White
(as Justiin Davis) |
| John Harrington Bland | Scotty Gulliver |
| Mike Houston | Ralph |
| Christina Jackson | Maybelle White |
| Will Janowitz | Hymie Weiss |
| Tom Kemp | |
| Randall McNeal | |
| J.C. Montgomery | (as JC Montgomery) |
| Brady Noon | Tommy Darmody |
| Connor Noon | Tommy Darmody |
| Balint Pinczehelyi | |
| Joseph Riccobene | Frankie Yale |
| G. Michelle Robinson | Mrs. Sybill Crawford |
| Christiane Seidel | Sigrid Mueller |
| Bob Sorenson | Dale |
| Dominique Swift | Adeline White |
| Natalie Wachen | Lenore White |
| Ryan Woodle | Phil |
| Maud Arnold | Onyx Club Dancer |
| Brittany Engel-Adams | Onyx Club Dancer |
| Karida Griffith | Onyx Club Dancer |
| Ayo Jackson | Onyx Club Dancer |
| Nicole J. Johnson | Onyx Club Dancer |
| Jennifer Jones | Onyx Club Dancer |
| Erin Moore | Onyx Club Dancer |
| Jae Ponder | Onyx Club Dancer |
| Celestine Rae | Onyx Club Dancer |
| Jennifer Rias | Onyx Club Dancer |
| Giuseppe Ardizzone | Capone Thug #1
(uncredited) |
| Mia Ciccarelle | Daughter
(uncredited) |
| Johnny DiGiorgio | Boardwalk Boy
(uncredited) |
| Kate Owens | High Class Girl
(uncredited) |
| Miranda Plant | Beachgoer
(uncredited) |
| Lynsey Leigh Price | High Class Girl
(uncredited) |
| Maria Shamkalian | Girl in Love
(uncredited) |