Season 4

=== Guest starring ===
* [[Louis Lombardi]] as [[Edgar Stiles]] (24 episodes)
* [[Arnold Vosloo]] as [[Habib Marwan]] (17 episodes)
* [[Mary Lynn Rajskub]] as [[Chloe O'Brian]] (16 episodes)
* [[Geoff Pierson]] as [[President]] [[John Keeler]] (13 episodes)
* [[Jonathan Ahdout]] as [[Behrooz Araz]] (12 episodes)
* [[James Frain]] as [[Paul Raines]] (10 episodes)
* [[James Morrison]] as [[Bill Buchanan]] (10 episodes)
* [[Nestor Serrano]] as [[Navi Araz]] (10 episodes)
* [[Cameron Bancroft]] as [[Lee Castle]] (9 episodes)
* [[Gregory Itzin]] as [[Vice President]]/[[President]] [[Charles Logan]] (9 episodes)
* [[Jude Ciccolella]] as [[Mike Novick]] (8 episodes)
* [[Logan Marshall-Green]] as [[Richard Heller]] (7 episodes)
* [[Aisha Tyler]] as [[Marianne Taylor]] (7 episodes)
* [[Angela Goethals]] as [[Maya Driscoll]] (5 episodes)
* [[Tony Plana]] as [[Omar (Day 4)|Omar]] (5 episodes)
* [[Leighton Meester]] as [[Debbie Pendleton]] (4 episodes)
* [[John Allen Nelson]] as [[Walt Cummings]] (4 episodes)
* [[Lukas Haas]] as [[Andrew Paige]] (3 episodes)
* [[Mia Kirshner]] as [[Mandy]] (3 episodes)
* [[Tomas Arana]] as [[Dave Conlon]] (2 episodes)
* [[Tzi Ma]] as [[Cheng Zhi]] (2 episodes) 
* [[Glenn Morshower]] as [[Aaron Pierce]] (2 episodes)
* and [[Shohreh Aghdashloo]] as [[Dina Araz]] (12 episodes)