The viewpoint character for much of the series, Parker is a former NYPD detective haunted (literally) by the murder of his wife and daughter.
- Atonement Detective: Parker is the embodiment of this trope.
- The Cameo: He makes one in Connolly's only non-Parker thriller, Bad Men.
- Cloudcuckoolander: Between his generally unhinged mental state following the murder of his family, and his increasing supernatural powers, it's hardly surprising that Parker has his moments.
- Cool Car: Owns several Mustangs over the course of the series.
- Dark and Troubled Past: Where to begin? When he was still a child his father, a respected NYPD cop, randomly killed two teenagers while on duty before committing suicide himself. His mother moved him back to Maine to live with her family, and died of cancer there when Charlie was a teenager. He was running afoul of thugs and gangsters when he was barely out of childhood, a habit he's carried on ever since. All that came before his wife and child were brutally murdered, which in turn happened before the series even started...
A semi-retired thief who has been aiding Parker since his time with the NYPD, and who owes the detective his life.
- Abusive Parents: His mother abandoned him when he was a baby, and his father sold him into prostitution from the age of eight.
- Badass Gay: Though not quite as badass as Louis - he's a terrible shot, for one thing - he definitely has his moments.
- He's also an ex-boxer, and seems to enjoy diverting himself by baiting homophobes in bars and then beating the crap out of them.
- Battle Couple: With Louis.
- Beware the Nice Ones: Angel is much more personable than either Parker or Louis. This does not mean he won't shoot you dead if you push him far enough.
- Big Damn Heroes: He often - though not always - accompanies Louis when the former is called upon to extract Parker from a situation he can't handle by himself.
- Break the Badass: He gets brutally tortured in The Killing Kind, an experience from which he never fully recovers.
- Dark and Troubled Past: In addition to his abusive father and horrific childhood, he was imprisoned a number of times as an adult, tortured by prison guards following a riot he had nothing to do with, and became the obsession of a psychotic rapist who was a fellow prisoner. Things picked up for him a bit when he met Parker and later Louis, but it doesn't always remain that way.
A semi-retired assassin, partner of Angel, whose guns and knowledge are frequently at Parker's disposal.
- Badass Gay: The "semi-retired assassin" thing pretty much speaks for itself.
- Battle Couple: With Angel.
- Big Damn Heroes: He frequently finds himself playing this role to Parker, often accompanied by Angel.
- Can't Bathe Without a Weapon: The White Road reveals that he and Angel first met when Angel broke into his apartment. Despite having just stepped out of the tub and wearing only a towel, Louis is able to pull a gun on him before he can get away.
- Cool Car: Owns a specially converted Lexus with, Parker estimates, enough firepower hidden in the trunk to create a small crater in the road if he hits a pothole too fast.
- Contract on the Hitman: His falling victim to this trope forms the main plot of The Reapers.
- Dark and Troubled Past: As a gay African-American growing up in the deep south of the '60s and '70s this is kind of a given, but it goes way beyond that. The man he suspects was his father was lynched by a group of racist thugs, and his mother and aunt were abused by a man who later murdered his mother, prompting the still-teenage Louis to kill him in revenge.
A psychiatrist, Parker's girlfriend and mother of his daughter, Sam. They separate in The Unquiet.
- Beware the Nice Ones: Though she's defined by her compassion and understanding, she will fight back if you threaten her or the ones she cares about, especially her unborn baby, as the antagonists in The White Road learn to their cost.
- Break the Cutie: This forms part of Rachel's character arc from the very start. It gets so bad by The Unquiet that she leaves Charlie for good at the end of the book.