| Dominic West | Det. James 'Jimmy' McNulty |
| Reg E. Cathey | Norman Wilson |
| John Doman | Dep. Comm. for Operations William A. Rawls |
| Aidan Gillen | Mayor Thomas 'Tommy' Carcetti |
| Clark Johnson | City Editor Augustus 'Gus' Haynes |
| Deirdre Lovejoy | Asst. State's Atty. Rhonda Pearlman |
| Tom McCarthy | Scott Templeton |
| Clarke Peters | Det. Lester Freamon |
| Wendell Pierce | Det. William 'Bunk' Moreland |
| Lance Reddick | Col. Cedric Daniels |
| Andre Royo | Reginald 'Bubbles' Cousins
(credit only) |
| Sonja Sohn | Det. Shakima 'Kima' Greggs |
| Seth Gilliam | Sgt. Ellis Carver
(credit only) |
| Domenick Lombardozzi | Thomas 'Herc' Hauk
(credit only) |
| Michael Kenneth Williams | Omar Little |
| Gbenga Akinnagbe | Chris Partlow |
| Jamie Hector | Marlo Stanfield |
| Neal Huff | Chief of Staff Michael Steintorf |
| Jermaine Crawford | Duquan 'Dukie' Weems |
| Corey Parker Robinson | Det. Leander Sydnor |
| Tristan Mack Wilds | Michael Lee
(as Tristan Wilds) |
| Michael Kostroff | Maurice 'Maury' Levy
(credit only) |
| Michelle Paress | Alma Gutierrez |
| Isiah Whitlock Jr. | State Sen. R. Clayton 'Clay' Davis |
| Frankie Faison | Commissioner Ervin H. Burrell |
| Paul Ben-Victor | Spiros 'Vondas' Vondopoulos |
| Robert F. Chew | Joseph 'Proposition Joe' Stewart |
| S. Robert Morgan | Butchie |
| Delaney Williams | Sgt. Jay Landsman |
| David Costabile | Managing Editor Thomas Klebanow |
| Sam Freed | Executive Editor James C. Whiting III |
| Bruce Kirkpatrick | Roger Twigg |
| Maria Broom | Marla Daniels |
| Al Brown | Dep. Comm. for Administration Stanislaus Valchek |
| Donnell Rawlings | Damien 'Day-Day' Price |
| Anwan Glover | Slim Charles |
| Method Man | Melvin 'Cheese' Wagstaff |
| Felicia Pearson | Felicia 'Snoop' Pearson |
| Michael Stone Forrest | Det. Frank Barlow |
| Todd Scofield | Jeff Price |
| Brandon Young | Mike Fletcher |
| Lenny Hamm | Det. Lenny Hamm |
| Ramon Rodriguez | Renaldo
(as Ramon Rodriquez) |
| Gregory L. Williams | Det. Michael Crutchfield |
| Donald Worden | Det. Donald Worden |
| Damon Henderson | Pastor |
| Thuliso Dingwall | Kenard |
| Kwame Patterson | 'Monk' Metcalf |
| Edward Bernard Green Jr. | Spider
(as Edward Green) |
| Keenon Brice | Aaron 'Bug' Manigault |
| Dominick Cicco | Andreas |
| Sarah Desage | Bank Teller |
| Michael Rivera | Renaldo's Friend |
| Baye C. Harrell | Hack Driver |
| Kristian King Lewman | Asst. Medical Examiner Diane Lerner |
| Eric Messner | Alma's Boyfriend |
| Joey Perillo | Medical Examiner Front Desk |
| Tracy Teague | McNulty's Date
(as Tracey Teague) |
| Vincent M. Ward | Butchie's Bodyguard |
| John Brennan | Banker #2
(as John Brennon) |
| Gary D'Addario | Grand Jury Prosecutor Gary DiPasquale |
| Sarah Grace Hart | Six Flags Girl #1 |
| Christine Lee | Store Clerk |
| Jim Scopelitis | Banker #1
(as Jim Scopeletis) |
| Sophia Wang | Six Flags Girl #2 |
| Michael Ahl | Detective
(uncredited) |
| Zach Book | The Sun Graphics Designer
(uncredited) |
| Anthony Bosco | The Sun Copy Editor
(uncredited) |
| Dave Cooperman | Ball Toss Contestant
(uncredited) |
| Kara Lee Duncan | Rebecca Corbett
(uncredited) |
| Dave Ehrman | Researcher
(uncredited) |
| Art Hall | Reporter
(uncredited) |
| Marshall Jefferies | Marlo's Lieutenant
(uncredited) |
| Steve Luxenberg | Sun Staff Member
(uncredited) |
| Elizabeth Mary Nolan | Reporter
(uncredited) |
| Robert Poletick | Steven Luxenberg
(uncredited) |
| Derrick Purvey | Big Guy
(uncredited) |
| Chad Ridgely | Justin Cook
(uncredited) |
| Jennifer Rouse | Whiting's Secretary
(uncredited) |
| Kevyn Settle | Sun Paper Layout Editor
(uncredited) |
| Patrick Michael Strange | Reporter
(uncredited) |
| Tom Townsend | Grand Juror
(uncredited) |
| Juan-Pablo Veizaga | CSI Police Officer
(uncredited) |