Portrayed by: Angie Harmon
- Action Girl: Rarely shies away from action. Even injured, she still wants to be the one to take people down.
- Adaptational Attractiveness: In the books that the series is based on, Jane Rizzoli is consistently described as plain or average looking. This is a significant characteristic, as she tends to have an irrational jealousy and dislike of beautiful women. She's also described at petite in stature, but here, she's being played by the tall and gorgeous Angie Harmon (though Harmon has played Jane as a little more rough and tumble as time went on).
- Aloof Dark-Haired Girl: Rizzoli is a tall, mature, dark haired woman.
- Ascended Extra: Rizzoli is actually a secondary character in "The Surgeon", the first book in the series, and author Gerritsen had planned to kill her off before positive reader feedback changed her mind.
- Berserk Button: Harm or threaten her family or Maura and she will show you why she's the top homicide detective in Boston PD.
- Brains and Brawn: The Brawn to Maura's Brains. While Maura prefers either to work in her lab or just quietly think things over, Jane prefers being out in the field and does not shy away from physical action.
- Deadpan Snarker: Sometimes in spite of herself. Even when she's around people she'd be better off not pissing off, she still can't help but snark at or about them.
- Embarrassing Middle Name: Clementine.
- Heterosexual Life-Partners: With Maura. They are almost inseparable, both at work and in their spare time, and Jane seems much closer to Maura than to her relatives or even to her lovers.
- Hidden Depths: Jane is actually rather good at ballet and chess.
- Impaled Palm: Jane still bears the scars from when The Surgeon literally pinned her hands to the ground.
- Inferiority Superiority Complex: In the books. Her abrasive personality and drive to succeed stems from feelings of inadequacy over her plain looks, plus years of being The Unfavorite both at home and on the job where's she's usually the only woman.
- Informed Attribute: Jane describes herself as strong and athletic even though Angie Harmon has the lithe, muscular frame of a toothpick. She might be telling the truth, but she sure doesn't look it.
- Limited Wardrobe: Usually to be found in a pantsuit and short-sleeved T-shirts.
- Meaningful Name: In the books. Jane is literally a "plain Jane".
- Middle Child Syndrome: She's usually overlooked by her mother in favour of older brother Tommy or little brother Frankie.
- Obfuscating Stupidity: It turns out she was accepted to BCU, but ended up not going because of her family situation. She also pretended not to know anything about chess when she was the one who taught Tommy how to play.
- Only Sane Woman: Jane qualifies, given how often the expression on her face resembles that of someone in the process of herding cats.
- Romantic Two-Girl Friendship: With Maura.
- Tomboy and Girly Girl: The Tomboy to Maura's Girly Girl.
- The Unfavorite: Angela always seemed to favor her boys over Jane, and even more so in the books.
- What Beautiful Eyes!: Noted by partner Thomas Moore in the first novel.
- What the Hell, Hero?: In the books. Gets called out on her irrational dislike of attractive women a handful of times. In particular, when Moore does it, he suggests that it might be her unattractive personality that turns men off, rather than her unattractive looks.
- Working-Class Hero: Her working-class background is often pointed out and contrasted to upper-class girl Maura.
Portrayed by: Sasha Alexander
- Adaptational Attractiveness: It's not as extreme a case as with Jane. Maura is described as "attractive" in the books, but as played by Sasha Alexander she is far more stunning than one would have imagined.
- Adaptation Dye-Job: Maura is an Eerie Pale-Skinned Brunette the books.
- All Women Love Shoes: Especially telling is her reaction when Jane quips that she hid her shoes. Oh, and she provides the page image.
- Ambiguously Bi: Even discounting the ton of Les Yay she has with Jane, she's put an awful lot of thought into what kind of women she'd be into if she were a lesbian, and she makes some comments that indicate that she wouldn't mind having sex with a woman.
- Ascended Extra: Isles doesn't exist at all in "The Surgeon", and when she makes an appearance (in "The Apprentice"), she's a minor character. From the third book ("The Sinner") onward, her role enlarges to be almost equal with Rizzoli in most books, or the primary character in several.
- Berserk Button: Go ahead, go after her shoe collection. See how far you get.
- And for the love of her fair metropolis, if Jane gets hurt...
- Brains and Brawn: The Brains to Jane's Brawn.
- Cannot Tell a Lie: Jane likes to point out what seems to be Maura's innate inability not to tell the truth. There are some exceptions where she actually doesn't tell the truth, or at least not the complete truth, but it is made clear that these are rare exceptions.
- The Coroner: Maura works as a medical examiner and her main field is forensic medicine - though being close to a universal genius she is shown doing other kinds of forensic science as well.
- Embarrassing Middle Name: Dorothea
- The Fashionista: Maura is very interested in fashion, always well dressed, and sometimes criticizes Jane's fashion choices and tries to improve the way she dresses.
- Good Bad Girl: Maura expresses a strong interest in sexual matters. Despite her somewhat shy, introverted personality and her nerdy image she seems to have a healthy sex life. See Really Gets Around.
- Heterosexual Life-Partners: With Jane. They are almost inseparable and seem to value each other's company above that of family or even their lovers.
- Hot for Preacher: In the books, becomes attracted to and eventually carries on an affair with a priest.
- Insufferable Genius: She doesn't do it on purpose, but it drives Jane batty nonetheless.
- Intelligence Equals Isolation: Maura reveals that her childhood wasn't exactly parties and ponies in "I'm Your Boogie Man." In her own words, "there was a lot of benign neglect" - her parents had their own lives to lead that frequently didn't involve the mundane details of parenthood, and they didn't much care what Maura did as long as she kept good grades. As a result, Maura buried herself in schoolwork, to the point that she gave them the brochures to send her away to boarding school. At ten years old.
- Morality Pet: A minor and not always effective one to her biological father Paddy Doyle Jr, a reputed mobster and killer. Paddy does seem to think she is the only good thing he's ever done and when his father, Paddy Sn. is getting ill, he asks Maura to help him get a compassionate release from prison and stay with Maura.
- Non-Idle Rich: Maura comes from a wealthy family and is financially independent. She works as a medical examiner because she loves her job, not to make a living.
- No Social Skills: While she does have some social skills, Maura is often somewhat awkward in social situations, and her rather blunt manner and inability to lie sometimes leads to embarrassing situations.
- Really Gets Around: She has had more partners than anyone else on the show, flirts with a man while examining a dead body, and pursued Giovanni solely to sleep with him.
- Screw the Money, I Have Rules!: Maura turning her back on the high society scene to work as a medical examiner. When Jane calls her out on her privileged background, she demonstrates quite convincingly that she "has [their] backs," using her connections to obtain several vital clues to the murder.
- Tomboy and Girly Girl: The Girly Girl to Jane's Tomboy.
Portrayed by: Jordan Bridges
- Embarrassing First Name: Francesco
Portrayed by: Bruce McGill
- Adaptational Attractiveness: Hardly a male model in his TV incarnation, but still much better looking than he's described in the books.
- Da Chief: After being promoted to Sergeant, Korsak is put in charge of a small team of detectives: himself, Rizzoli and Frost.
- Friend to All Living Things: Korsak is constantly rescuing animals.
- Like A Daughter To Me: His relationship with Jane.
- Theme Naming: He has dogs named Starsky, Hutch, and Kojak.
- The Mentor: To Jane.
- Papa Wolf: Towards Jane.
Portrayed by: Lee Thompson Young
- Actor Existence Failure: The unfortunate suicide of Lee Thompson Young.
- Afraid of Blood: Especially in the first season, Frost's squeamishness and physical discomfort at the sight of blood and dead bodies makes him the butt of many jibes from his more hardened colleagues.
- Black and Nerdy: Frost is well versed in computer technology, action figures, and MMORPGs.
- Embarrassing First Name: Barold.
- Has Two Mommies: His mom and roommate come to town. The others figure out they are a couple, but are afraid to say anything. Turns out he knew all along, was just waiting for his mom to say something.
- Killed Off for Real: Dies in a car accident, due to the real life suicide of his actor...
- Race Lift: Detective Frost is white in the books, African-American in the TV series.
- Token Minority: The only black member of the main cast.
- Vomiting Cop: Especially in the first season, he's easily nasueated by gore and dead bodies. This is often justified since some of the corpses have been decomposing for a while, but the other cops have become used to such things. He seems to be getting better about it, though.
Portrayed by: Lorraine Bracco
- Amazingly Embarrassing Parents: Even though Jane is in her thirties, she still often finds her mother's behaviour embarrassing.
- Big Secret: She was going around taking up any odd job she could find and acting funny any time money is mentioned. Her husband cheated on their taxes and left her holding a $27,000 debt. She doesn't want to let Jane and Frankie know so she can keep him looking good for them, but they find it out.
- My Beloved Smother: She is very protective of her grown-up children, who often are more than a little embarrassed or irritated at what they perceive as her attempts to control their lives.
- Parental Favoritism: Jane is blatantly ignored in favor of her brothers, especially Frankie.
- Parental Substitute: To Maura.