| Dominic West | Off. James 'Jimmy' McNulty |
| Chris Bauer | Frank Sobotka |
| Paul Ben-Victor | Spiros 'Vondas' Vondopoulos |
| John Doman | Col. William A. Rawls |
| Idris Elba | Russell 'Stringer' Bell |
| Wood Harris | Avon Barksdale |
| Deirdre Lovejoy | Asst. State's Atty. Rhonda Pearlman |
| Clarke Peters | Det. Lester Freamon |
| Wendell Pierce | Det. William 'Bunk' Moreland |
| Lance Reddick | Lt. Cedric Daniels |
| Amy Ryan | Off. Beatrice 'Beadie' Russell |
| Sonja Sohn | Det. Shakima 'Kima' Greggs |
| Seth Gilliam | Sgt. Ellis Carver |
| Domenick Lombardozzi | Det. Thomas 'Herc' Hauk |
| Jim True-Frost | Det. Roland 'Prez' Pryzbylewski |
| James Ransone | Chester 'Ziggy' Sobotka |
| Pablo Schreiber | Nick Sobotka |
| Al Brown | Maj. Stanislaus Valchek |
| Melanie Nicholls-King | Cheryl |
| J.D. Williams | Preston 'Bodie' Broadus |
| Delaney Williams | Sgt. Jay Landsman |
| Chris Ashworth | Sergei 'Serge' Malatov |
| Luray Cooper | Nathaniel 'Nat' Coxson |
| Jeffrey Fugitt | Claude Diggins |
| Bill Raymond | The Greek |
| Teddy Cañez | George 'Double G' Glekas |
| Tel Monks | Father Jerome Lewandowski |
| The Nighthawks | The Nighthawks |
| Elisabeth Noone | Joan Sobotka |
| Charley Scalies | Thomas 'Horseface' Pakusa |
| Harold J. Abell Sr. | Moonshot |
| Jennifer Badger | Slavic Drowning Victim |
| Perry Blackmon | Perry |
| Richard Burton | Sean 'Shamrock' McGinty |
| Jeffrey Coleman | Coast Guard Officer |
| Robert F. Colesberry | Det. Ray Cole |
| Jeffrey Pratt Gordon | John 'Johnny Fifty' Spamanto |
| J. Valenteen Gregg | Chess |
| De'Rodd Hearns | Herbert De'Rodd 'Puddin' Johnson |
| Bus Howard | Vernon 'Ott' Motley |
| Kevin Jiggetts | Frommers |
| Doug Lory | Big Roy |
| Amber Nelson | Yacht Waitress |
| Jeremy Nichols | First Mate |
| Richard Pelzman | Little Big Roy |
| David Peters | Diener |
| Jonathan Pope | Sergeant |
| Jill Redding | Delores |
| Addison Switzer | Country |
| Rico Whelchel | Rico |
| Jonathan D. Wray | Tank |