Recurring
Thomas Lennon as Leo Getz, a comedic ambulance-chasing lawyer who once worked in the District Attorney's office before being fired. He befriends Riggs and Murtaugh after he witnesses a client's murder, and is put under their protection. He quickly takes a liking to them and their friendship strengthens by the second season. He was originally played by Joe Pesci in the film series.
Hilarie Burton as Karen Palmer (seasons 1–2), a DEA agent who sometimes works with Riggs and Murtaugh on drug trafficking cases, and is also Riggs' love interest. The two break up early in season 2.
Floriana Lima as Miranda Riggs (née Delgado) (seasons 1–2), Det. Riggs' late wife, who is seen in flashbacks. Originally from the Los Angeles area, she moved to Texas when she married Riggs, and after her death, he moved to LA and joined the LAPD. The character is based on Victoria Riggs from the film series, although she was never seen as she had already died before the events of the first film.
Richard Cabral as Detective Alejandro "Alex" Cruz (season 1), formerly an undercover officer with the LAPD's Gang Division who once worked at the Robbery-Homicide Division.
Tony Plana as Ronnie Delgado (seasons 1–2), the Los Angeles City Attorney and Det. Riggs' father-in-law. He is stabbed in prison in the Season 2 episode "Diggin' Up Dirt", and dies in the hospital.
Andrew Patrick Ralston as Jim McNeile, a dentist and neighbor of the Murtaughs.
Michelle Hurd as Gina Santos (seasons 2–3), a police big shot who arrives to take control of the division as chief, superseding the authority of Captain Avery. She and Murtaugh had previously partnered as detectives on a stakeout.
Andrew Creer as Detective Zach Bowman (season 2), a young detective who starts working at the precinct. He is soon partnered with Bailey. Leo Getz condescendingly calls them "The B-team", which the naïve Bowman thinks is because their last names both start with "B".
Kristen Gutoskie as Molly Hendricks (season 2), Riggs' childhood friend and the ex-wife of his old best friend Jake, who has been in and out of prison. Riggs and Molly have a brief relationship that Riggs ends when he sees his work and his father are putting Molly and her son in danger. They later are able to reconcile, and make plans to move back to Texas together just before Riggs is shot in the season 2 finale.
Rex Linn as Nathan Riggs (season 2), Riggs' abusive father
Chase Mangum as Young Martin Riggs (season 2)
Sophia Woodward as Young Molly Hendricks (season 2)
Duncan Joiner as Ben (season 2), Molly's son via her ex-husband Jake
Peter Coventry Smith as Garrett Riggs (seasons 2–3), Riggs' much younger half-brother and killer
Maggie Lawson as Natalie Flynn (season 3), Cole's ex-wife
Shay Rudolph as Maya Flynn (season 3), Cole and Natalie's daughter
Mykelti Williamson as Tom Barnes (season 3), Cole's former commanding officer
Paola Lázaro as Detective Luisa "The Gute" Gutierrez (season 3), Detective Sonya Bailey's new partner
Nishi Munshi as Erica Malick (season 3), a deputy district attorney and potential love interest for Cole