Main cast •
Kevin Bacon as Ryan Hardy, a former
FBI agent, recalled to assist the FBI once Joe Carroll escapes and begins to develop his cult •
Jeananne Goossen as Jennifer Mason (pilot), an FBI agent who is replaced by Debra Parker after the pilot episode •
Natalie Zea as Claire Matthews (seasons 1–2), Joe Carroll's ex-wife, who also had a relationship with Ryan Hardy •
Annie Parisse as Debra Parker (season 1), head of the investigation on Joe Carroll and his cult •
Shawn Ashmore as Mike Weston, a young FBI agent who later becomes romantically involved with Ryan's niece, Max •
Valorie Curry as Emma Hill (seasons 1–2), a follower and romantic partner of Joe Carroll •
Nico Tortorella as Jacob Wells (season 1), one of Joe Carroll's followers and romantic interest of both Emma and Paul •
Adan Canto as Paul Torres (season 1), one of Joe Carroll's followers, working closely with Jacob and Emma •
Kyle Catlett as Joey Matthews (season 1), Joe Carroll and Claire Matthews' son •
Maggie Grace as Sarah Fuller (pilot), Joe Carroll's last victim before his capture •
James Purefoy as Joe Carroll, a former professor turned serial killer and cult leader •
Sam Underwood as Luke and Mark Gray (seasons 2–3), Lily's psychopathic twin sons •
Jessica Stroup as Max Hardy (seasons 2–3), niece of Ryan Hardy and a
New York City Police Department detective •
Tiffany Boone as Mandy Lang (season 2), daughter of Judy, an admirer and daughter-figure to Joe Carroll who gets caught between him and Lily •
Connie Nielsen as Lily Gray (season 2), cult leader, admirer of Carroll, and mother of Luke and Mark •
Zuleikha Robinson as Gwen (season 3), an emergency room physician and Ryan Hardy's girlfriend •
Gregg Henry as Arthur Strauss (recurring season 2; starring season 3), a doctor and Joe Carroll's mentor who introduced him to killing •
Michael Ealy as Theo Noble (season 3), a follower of Dr. Strauss and a genius computer hacker. Strauss considers him his best student
Recurring cast • John Lafayette as Scott Turner (seasons 1–3), head of the Marshals' detail participating in the investigation of Joe Carroll's cult, later provides protection for Claire Matthews •
Afton Williamson as Haley Mercury (season 1, guest star season 3), owner of an online fetish site who assists Ryan Hardy in tracking Joe Carroll's and Mark Gray's followers •
Valerie Cruz as Gina Mendez (seasons 2–3), an FBI agent who is head of the investigation on Joe Carroll and the new cults formed a year after his supposed death •
Mike Colter as Nick Donovan (seasons 1 & 3), an FBI agent who assumes command of the FBI team following Joe Carroll's second escape from prison •
Felix Solis as Jeff Clarke (seasons 2–3), an FBI special agent and Ryan Hardy's direct liaison to the director of the FBI
Season 1 •
Billy Brown as Troy Riley, an FBI agent who initially assisted Ryan Hardy in the days following Joe Carroll's escape from prison • Chinasa Ogbuagu as Deirdre Mitchell, an FBI agent, specializing in following and tracking cult information on the computer •
Michael Drayer and Virginia Kull as Rick and Maggie Kester, followers of Joe Carroll •
Li Jun Li as Megan Leeds, hostage of Paul, Jacob, and Emma •
Warren Kole as Tim "Roderick" Nelson, Joe Carroll's friend and second in command of the cult •
Annika Boras as Louise Sinclair, follower of Joe Carroll and love interest of Roderick •
Jennifer Ferrin as Molly, one of Joe Carroll's followers, planted to develop a romantic relationship with Ryan Hardy •
Renée Elise Goldsberry as Olivia Warren, Joe Carroll's attorney •
Tom Lipinski as Charlie Mead, an ex-militant and member of Joe Carroll's cult assigned to stalk Claire Matthews in the years following Joe Carroll's incarceration •
Christopher Denham,
Steve Monroe, and
Arian Moayed as Vince McKinley, Jordy Raines, and David, followers of Joe Carroll
Season 2 •
Carrie Preston as Judy Lang, admirer of Joe Carroll with whom he lives for a year after going into hiding •
Camille De Pazzis as Giselle, adoptive daughter of Lily Gray. •
Bambadjan Bamba, Hugues Faustin and Rita Markova as Sami, Jamel and Radmilla, Lily Gray's adopted children •
Jake Weber and
Jacinda Barrett as Micah and Julia, the leaders of the Korban cult •
Shane McRae, Mackenzie Marsh, Josh Salatin, and Liza de Weerd as Robert, Tilda, Lucas, and Angela, members of the Korban cult •
Leslie Bibb as Jana Murphy, a retired FBI agent, Gina's ex-girlfriend and a friend and helper of Joe Carroll •
Tom Cavanagh as Kingston Tanner, televangelist who denounces Joe Carroll •
Carter Jenkins as Preston Tanner, Kingston's son •
Sprague Grayden as Carrie Cooke, a tabloid reporter with an on-and-off relationship with Ryan Hardy
Season 3 •
Michael Irby as Andrew Sharp, ex-student of Arthur Strauss •
Gbenga Akinnagbe as Tom Reyes, Max's boyfriend who is also member of the
FBI Hostage Rescue Team •
Ruth Kearney as Daisy Locke, ex-student of Arthur Strauss •
Monique Gabriela Curnen as Erin Sloan, an FBI tech analyst •
Hunter Parrish as Kyle Locke, ex-student of Arthur Strauss •
Glenn Fleshler as Neil Perry, ex-student of Arthur Strauss •
Anna Wood as Juliana Barnes, lawyer of Arthur Strauss •
Tim Guinee as Duncan Banks, ex-student of Arthur Strauss •
Susan Kelechi Watson as Cindy Noble, Theo's wife •
Megalyn Echikunwoke as Penny Tyler, Theo's adopted sister •
Diane Neal as Lisa Campbell, an FBI agent •
Annet Mahendru as Eliza ==Production==