Kiefer Sutherland: Jack -- Head of the government's Counter Terrorism Unit, Teri's husband and Kimberly's dad
Elisha Cuthbert: Kimberly -- High school student, daughter of Jack and Teri
Dennis Haysbert: David -- Senator from Maryland, running for President, Sherry's husband, Keith and Nicole's father
Penny Johnson Jerald: Sherry -- David's wife and mother to Keith and Nicole
Vicellous Reon: Keith -- David and Sherry's son, Nicole's brother
Megalyn Echikunwoke: Nicole -- David and Sherry's daughter, Keith's sister
Sarah Clarke: Nina Myers -- Had a fling with Jack, now dating Tony, ranks higher than Tony, CTU mole
Karina Arroyave: Jamey Farrell -- Another operative, killed by Nina
Carlos Bernard: Tony Almeida -- Dating Nina, jealous of her relationship to Jack
Michael O'Neill: Richard Walsh -- Jack's boss and mentor, died in Hour 2
Eric Balfour: Milo -- an outside contractor
Tamara Tunie: Alberta Green -- brought in to replace Jack, has a past history with Nina
Paul Schulze: Ryan Chappelle -- FBI agent who questions Jack in Hour 14.
Xander Berkeley: George Mason -- In charge at CTU after Jack is relieved of his duties. Jack shoots him with a tranquilizer dart in Hour 1.