Main •
Chyler Leigh as Detective Caitlin Mary Darcy "Cat" Sullivan, a second-generation, Irish-American detective with the fictional 125th Precinct (in reality, the precinct that serves the
Prospect Park area is the 78th Precinct). She achieved some level of notoriety after capturing the "Prospect Park Stalker". After her driving privileges are suspended, she commandeers Leo Romba, a French taxi driver, to become her personal valet. She is recently divorced from FBI Special Agent Gregg James. She attended Catholic school, where she was starting point guard during her senior year on both her school's All-City and All-State teams, but is now a
lapsed Catholic. Growing up, she was best friends with Annabella Capella (
Justine Cotsonas), the granddaughter of the head of the Capella crime family who has since taken over the family business. She is highly uncomfortable with her mother's affair with the police captain. Her late father was a
dirty cop on the Capella family's payroll, who murdered Annabella's grandfather to escape an Internal Affairs investigation, and was killed in revenge. •
Jacky Ido as Leo Romba, a Brooklyn cab driver from
Marseille, France, who becomes Cat's driver and a consultant for the 125th Precinct. He spent four years in a French prison for serving as a getaway driver; he testified against the robbers and spent two years in
solitary confinement. As a result, Leo has developed
claustrophobia. He has a son, Nico, that he loves very much, and an ex-wife, Aimee, who has since remarried. He considers Frankie (Cat's mother) a close friend. In "Revenge", it is revealed that Aimee is separated from her new husband; she and Nico are kidnapped immediately after their arrival in New York by Leo's former partner-in-crime, Henry. • James Colby as Captain John Baker, the commander of the 125th Precinct. He is Cat's godfather, and recently he has begun an affair with her mother. •
José Zúñiga as Detective Eddie Esposito, Cat's co-worker and rival at the 125th Precinct. •
Jennifer Esposito as Dr. Monica Pena, a medical examiner with the Brooklyn Borough
Office of the Chief Medical Examiner and a friend of Cat's. • Bill Heck as Special Agent Gregg James, an FBI agent and Cat's ex-husband. In "Revenge", he is shot by a Capella family shooter. •
Ally Walker as Frankie Sullivan, Cat's widowed mother. She and Leo are good friends. • Raul Casso as Ronnie, a fellow cab driver and a close friend of Leo's; notable for a mock-flamboyant personality.
Recurring •
Luke Roberts as Rhys •
Caterina Murino as Giada