Police
Barksdale Detail
- Jimmy McNulty - case driven but insubordinate detective
- Cedric Daniels - narcotics shift lieutenant and detail commander
- Kima Greggs - narcotics detective and Daniels' protege
- Thomas "Herc" Hauk - narcotics detective with a penchant for physical policing
- Ellis Carver - Ambitious narcotics detective
- Roland "Prez" Pryzbylewski - Notoriously unreliable detective
- Leander Sydnor - Young detective from auto crime
- Lester Freamon - Elder detective from the pawn shop unit
- Michael Santangelo - White haired detective from homicide!
- Augustus Polk - Alcoholic detective from property
- Patrick Mahone - Older detective from property
Command
- Warren Frazier - Commissioner
- Ervin Burrell - Deputy Commissioner of Operations
- William Rawls - Major and Homicide Unit Commander
- Raymond Foerster - Major and Narcotics Unit Commander
- Stanislaus Valchek - Major and South Eastern District Commander
- Bobby Reed - Major and Internal Investigations Division Commander
Homicide
- Jay Landsman
- Bunk Moreland
- Ray Cole
- Ed Norris
- Vernon Holley
- Frank Barlow - primary detective in the Pooh Blanchard case
Others
- Troy Wiggins - state police narcotics detective
- Bobby Brown - Western district uniform whose beat includes the Barksdale organization's territory
- Randall Frazier - Baltimore city medical examiner
- Walter Cantrell - commander of Prez and Sydnor's unit
- Torret - leader of the department's Quick Response Team
- Terrance "Fitz" Fitzhugh - a friend of McNulty's and an FBI Agent
- Amanda Reese - FBI Supervisor
- Arnold D. Paulette - a senior FBI Agent
Relatives
- Cheryl - Greggs' domestic partner
- Marla Daniels - Cedric Daniels' wife
- Elena McNulty - Jimmy McNulty's estranged wife
- Sean McNulty - Jimmy McNulty's oldest son
- Michael McNulty - Jimmy McNulty's youngest son
Courthouse
- Judge Daniel Phelan - Baltimore circuit court judge
- ASA Rhonda Pearlman - head of narcotics prosecution
- ASA Ilene Nathan - head of violent crimes prosecution
- ASA Taryn Hansen - prosecutor in the D'Angelo Barksdale trial
- ASA Dawkins - prosecutor in the Marvin Browning trial
- AUSA Nadiva Bryant - federal prosecutor with the FBI
- Defense Attorney Maurice Levy - the Barksdale's lawyer
Barksdale organization
- Avon Barksdale - drug kingpin
- Russell Bell aka Stringer - Avon's second
- D'Angelo Barksdale aka D - crew chief
- Roland Brice aka Wee-Bey - chief enforcer
- Anton Artis aka Stinkum - an enforcer and lieutenant
- Marquis Hilton aka Bird - a foul mouthed enforcer
- Savino Bratten - a young enforcer
- Wintell Royce aka Little Man - an enforcer at the Franklin Terrace high rises
- Wendell Blocker aka Orlando - front owner of the Barksdale's strip club
- Wallace - a young dealer at the Franklin Terrace low rises
- Preston Broadus aka Bodie - a young drug dealer at the Franklin Terrace low rises
- Malik Carr aka Poot - a young drug dealer at the Franklin Terrace low rises
- Sterling - a young drug dealer at the Franklin Terrace low rises
- Cass - a young drug dealer at the Franklin Terrace low rises
- Herbert De'Rodd Johnson aka Puddin - a young drug dealer at the Franklin Terrace high rises
- Kevin Johnston - a young drug dealer at the Franklin Terrace high rises
- Ronnie Mo - a crew chief
- Marvin Browning - a mid-level drug dealer
- Roc Roc - a a mid-level drug dealer
- CCO - a a mid-level drug dealer
- Perry - a bodyguard
- Donette - D'Angelo's girlfriend
- Chantal - Avon's girlfriend
- Brianna Barksdale - Avon's sister
Omar's crew
- Omar Little - a homosexual stick-up man, who robs the dealers
- Brandon Wright - Omar's romantic and criminal partner
- John Bailey - the third member of Omar's crew
Others
- Clay Davis - a corrupt State Senator
- Damien Lavelle Price - an aide to Senator Davis
- William Gant - a maintenance man and witness in D'Angelo's trial
- Nakeesha Lyles - a security guard and witness in D'Angelo's trial
- Scar - Stinkum was killed by Omar trying to take away Scar's corner
- Keisha - a stripper at Orlando's
- Shardene Innes - a stripper at Orlando's that dates D'Angelo
- Bubbles - drug addict, confidential informant and friend of Kima
- Johnny Weeks - drug addict
- Hucklebuck - drug addict
- Rae - Bubbles' sister
- Walon - recovering drug addict
- Mrs. Broadus - Bodie's Grandmother
- Mrs. Bratton - Savino' mother
- Darcia Wallace - Wallace's mother
- Deirdre Kresson - a murder victim found in her appartment
- Tywanda - a friend of Deirdre Kresson
- Pooh Blanchard - murdered by D'Angelo Barksdale
- Taureen Boyd - a murder victim
- Roland Leggett - a murder victim
- Bill Zorzi - a journalist with The Baltimore Sun
- Madame LaRue - a psychic with experience in death investigations
- Roy Brown - an ex-partner of Freamon's