- Rusty Beck (Graham Patrick Martin): Sharon Raydor's adoptive son, a former prostitute who witnessed Phillip Stroh committing murder. He has since started a investigative video blog called Identity.
- Assistant Chief Russell Taylor (Robert Gossett): Assistant Chief of Operations until Season 5 episode "White Lies, Part 1". He is Captain Raydor's immediate supervisor. The former commander of Robbery-Homicide Division, and later press liaison for Major Crimes, Taylor long felt passed over and unappreciated.
- Deputy Chief Fritz Howard (Jon Tenney): Fritz Howard was an special agent for the F.B.I. and the liaison officer to the LAPD (The Closer and Major Crimes, Seasons 1 and 2). Upon his retirement, he is recruited to head the LAPD's Special Operations Bureau, and assumes the rank of Deputy Chief (Major Crimes, Season 3 onward). He is currently the Acting Director of Operations until a replacement for Assistant Chief Taylor can be found.
- Captain Sharon Raydor (Mary McDonnell): The commanding officer of Major Crimes Division.
- Lieutenant Louie Provenza (GW Bailey): The division's senior member and Sharon's second-in-command. He is the immediate supervisor of the team in the field.
- Lieutenant Andy Flynn (Anthony Denison): Provenza's partner.
- Lieutenant Michael Tao (Michael Paul Chan): The squad's forensics and technology expert; Tao previously was assigned to the LAPD's Scientific Investigation Division (SID).
- Detective Julio Sanchez (Raymond Cruz): The squad's gang and weapons expert, experience gained from his days on the LAPD's gang intelligence unit.
- Detective Amy Sykes (Kearran Giovanni): Transferred from the Special Investigation Section of Robbery-Homicide, she is an expert on undercover operations. Sykes is a military veteran who served in Afghanistan.
- Detective Wes Nolan (Daniel DiTomasso): Det. Nolan was transferred to the division after ending his SIS undercover assignment.
- Civilian Surveillance Coordinator Buzz Watson (Phillip P. Keene): Buzz is the Scientific Investigation Division's civilian investigator assigned to the division. He is responsible for memorializing crime scenes, and managing technology in the field and in the squad's office. He also recently qualified as an LAPD reserve police officer.
- Dr. Fernando Morales (Jonathan Del Arco): A Los Angeles County Deputy Medical Examiner who coordinates with the team, conducting autopsies. Morales has a sharp medical mind and and equally sharp, sometimes sarcastic, wit. Morales is gay, and provides expertise on the gay community in Los Angeles.
- Investigator Kendall (Ransford Doherty): Kendall is responsible for examining the body at the crime scene and taking initial measurements, as well as preparing the body for transportation to the Los Angeles County Coroner's office.
- Deputy District Attorney Andrea Hobbs (Kathe Mazur): The DDA who works most frequently with Major Crimes, Hobbs is a team player.
- Deputy District Attorney Emma Rios (Nadine Velazquez): A new, inexperienced DDA under Hobbs' supervision, she is charged with preparing the case against Phillip Stroh (Season 2).
Recurring characters Edit
- Commander Ann McGinnis (Laurie Holden): Commander McGinnis is the second-in-command of the LAPD's Special Operations Bureau.
- Lieutenant Chuck Cooper (Malcolm-Jamal Warner): Lieutenant Cooper is the commanding officer of the Special Investigation Section (SIS) of the LAPD.
- Detective Robert Oderno (Brandon Barash): Robert Oderno is a detective in the LAPD's Missing Persons Unit.
- Gustavo Wallace (Rene Rosado): Gus Wallace is the older brother of murder victim Mariana Wallace. He is currently dating Rusty Beck.
- Deputy Chief Winnie Davis (Camryn Manheim): Chief Davis is a Deputy Chief of Operations for the LAPD and one of the candidates to replace Chief Taylor as the new Director of Operations (Season 5 winter episodes).