Main
Thandiwe Newton (credited as Thandie Newton) as Grace Travis (main seasons 1–2, recurring season 3): a rogue undercover cop whose career path has taken a toll on her personal life. She is Evie's mother and estranged wife of Tom.
Sarah Jeffery as Evie Travis (main seasons 1–2, recurring season 3): Grace's feisty but caring teenage daughter.
Kavan Smith as Tom Travis (seasons 1–2): Grace's ex-husband.
Ian Tracey as Lucas "Mitch" Mitchel (season 1): Detective of the Santa Fe PD investigating Sam Travis death. He helps her investigate "off-book", and is one of Grace's only long-term friends.
Marton Csokas as Jimmy Laszlo (season 1): Head of the Laszlo family, and known mob leader.
Joshua Sasse as Alec Laszlo (season 1, recurring season 2): First son of Jimmy Laszlo with a violent history.
Matthew Beard as Max Laszlo (season 1): Jimmy Laszlo second son, business school graduate, just released from prison.
Leah Gibson as Cathy Laszlo (season 1): Wife of Alex Laszlo.
Ian Hart as Buddy Wilson (season 1): An Oakland PD detective with an unconventional investigating method who helps Grace and Mitch.
Jarod Joseph as Nicholas Fleming (season 1): A young detective of the Oakland Police Department.
Claudia Ferri as Sophia Hernandez (season 1): Lieutenant of the Oakland Police Department.
Cole Hauser as Ethan Kelly (seasons 2–4): a college-educated ex-soldier who, as an overseas military contractor, was the leader of a gang of four who stole a large sum of money from the U.S. government. At the end of series two he is blackmailed by the general who catches him and decides to work for the general (series three) rather than confess and expose the conspiracy. In the fourth season he falls into a hellish labyrinth of criminality and betrayal by the police.
Andrea Roth as Leni Kastner (season 2): An FBI Special Agent and second in command in the task force, she is Grace's handler. She continues to believe in Grace and is instrumental in exposing the conspiracy. Ultimately she turns against Grace, deciding to not expose the conspiracy and cover-up.
Clare Higgins as Vivian Travis (season 2): Grace's estranged mother.
Alec Newman as Ray Williams (season 2): A member of Ethan Kelly's platoon.
Brendan Fletcher as Brian "Spud" Cacelle (season 2): A member of Ethan Kelly's platoon, he has PTSD.
Cindy Sampson as Sophie Hale (season 3).
Sarah Carter as DEA Agent Harper Deakins (season 3): A member of a federal task force formed to control Chicago's gang problem whose unwillingness to back down exposes a vast conspiracy. She is killed by Mia.
Derek Luke as Marlon Dinard (season 3): a respectable owner of a chandelier store who is also the head of a Chicago gang
Bianca Lawson as Talia Freeman (season 3): Marlon's half-sister who seeks to make a name for her own self, but her rash behavior constantly draws Marlon's attention
Michael Murphy as George Kelly (season 3): Ethan's father.
Richard Schiff as Marty Stein (main season 3, recurring season 4): a powerful Chicago lawyer that represents CEOs, judges, the Chicago Bulls, and mobsters, while having them all in his back pocket.
Ashley Greene as Mia Rochland (seasons 3–4): in season four Mia seeks revenge and will stop at nothing to make Ethan pay for double-crossing her. She was shot by Sadie and later killed by Patrick.
Sergio Di Zio as Patrick Finnegan (seasons 3–4): A Chicago police detective, Harper Deakins' partner on the federal task force. Seeks revenge on Mia for Harper's death.
Meaghan Rath as Clea Annou (season 4): a sharp San Francisco police detective with relentless dedication to her job and her family.
Neal McDonough as Casey Oaks (season 4): a dirty detective in San Francisco, working in support of Ombello.
Kristin Lehman as Theresa Archer (season 4): Ombello's CEO, a management consultant firm who provides trafficked girls to their clients.
