| 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
(credit only) |
| Michael Kenneth Williams | Chalky White |
| Anthony Laciura | Eddie Kessler
(credit only) |
| Paul Sparks | Mickey Doyle |
| Jack Huston | Richard Harrow |
| Ron Livingston | Roy Phillips
(credit only) |
| Jeffrey Wright | Valentin Narcisse |
| Gretchen Mol | Gillian Darmody |
| Patricia Arquette | Sally Wheet |
| Dominic Chianese | Leander Cephas Whitlock |
| Brian Geraghty | Agent James M. Tolliver /
Warren Knox |
| Domenick Lombardozzi | Ralph Capone |
| Ben Rosenfield | Willie Thompson |
| Wrenn Schmidt | Julia Sagorsky Harrow |
| Eric Ladin | Director J. Edgar Hoover |
| Margot Bingham | Daughter Maitland |
| Greg Antonacci | Johnny Torrio |
| Kevin O'Rourke | Mayor Edward Bader |
| Tim Ransom | Victor Drake - Defense Attorney |
| Katherine Waterston | Emma Harrow McCready |
| Gregory Abbey | |
| Steven L. Barron | Vocal Reporter |
| Gregory Bastien | |
| Steve Beauchamp | Sid - Nucky's Bodyguard |
| Mark Borkowski | Paul Sagorsky |
| Joseph Anthony Byrd | Sterling |
| Joe Caniano | Jake Guzik |
| Brian D. Coats | Levi |
| Danny Doherty | |
| Thomas Endres | Philadelphia Enquirer Reporter |
| Josie Gallina | Emily Schroeder |
| Lucy Gallina | Emily Schroeder |
| Madeline Getty | Nora Thompson |
| Chris Anthony Giles | Clarence Williams |
| Terry Greiss | |
| Ria Gusman | |
| Brian Tyree Henry | Winston aka Scrapper |
| Emma Holzer | Edith Thompson |
| Christina Jackson | Maybelle White |
| Jacob Knoll | Police Officer #1
(as Jacob H. Knoll) |
| Anna Mancini | Dancer |
| Michael X. Martin | Police Officer #2 |
| Matt McDonald | Agent Beagan |
| David McElwee | Roger's Friend |
| Declan McTigue | Teddy Thompson |
| Rory McTigue | Teddy Thompson |
| Brady Noon | Tommy Darmody |
| Connor Noon | Tommy Darmody |
| Charlie Plummer | Michael Thompson |
| Jay Russell | Prosecutor |
| Nisi Sturgis | June Thompson |
| Sebastian Tillinger | Hubert McCready |
| Jacob A. Ware | Agent Harold Selby |
| Brandon Zumsteg | Brian Thompson |
| Chloe Arnold | Onyx Club Dancer |
| Maud Arnold | Onyx Club Dancer |
| Brittany Engel-Adams | Onyx Club Dancer |
| Afra Hines | Onyx Club Dancer |
| Ayo Jackson | Onyx Club Dancer |
| Nicole J. Johnson | Onyx Club Dancer |
| Jennifer Jones | Onyx Club Dancer |
| Jennifer Locke | Onyx Club Dancer |
| Marla McReynolds | Onyx Club Dancer |
| Vivian Nixon | Onyx Club Dancer |
| Jae Ponder | Onyx Club Dancer |
| Celestine Rae | Onyx Club Dancer |
| Jennifer Rias | Onyx Club Dancer |
| Norman Aaronson | Court Reporter
(uncredited) |
| Peter Conboy | Court Officer
(uncredited) |
| Emma Cooper | Cicero Prostitute
(uncredited) |
| Richard R. Corapi | Patient in Wheelchair
(uncredited) |
| Liam Ferguson | Sheriff's Deputy
(uncredited) |
| Joe Fionda | Federal Agent
(uncredited) |
| Heather Gilbert | Prostitute
(uncredited) |
| Matthew Gooley | Newspaper Reporter
(uncredited) |
| Brian Kealty | Federal Agent
(uncredited) |
| Cal Koury | Nucky Thompson Bodyguard
(uncredited) |
| Paul Jude Letersky | NJ State Police Officer
(uncredited) |
| Jerry Lobrow | FBI Agent
(uncredited) |
| Rachael Ma | Onyx Club Smoker
(uncredited) |
| Frank L. Messina | Frankie
(uncredited) |
| Sarah Middlemiss | Onyx Upperclass Patron
(uncredited) |
| Lamar Richardson | Onyx Club Dancer
(uncredited) |
| Dion Sapp | Narcisse Thug
(uncredited) |
| Gary Schnakenberg | Court Gallery
(uncredited) |
| Alonzo Wright | Onyx Club Musician
(uncredited) |