Mark Harmon NCIS Special Agent Leroy Jethro Gibbs Actor, Executive Producer Sean Murray NCIS Special Agent Timothy McGee Actor Wilmer Valderrama NCIS Special Agent Nicholas "Nick" Torres Actor Brian Dietzen Dr. Jimmy Palmer Actor Diona Reasonover Forensic Scientist Kasie Hines Actor Katrina Law NCIS Special Agent Jessica Knight Actor Rocky Carroll NCIS Director Leon Vance Actor, Director David McCallum Dr. Donald "Ducky" Mallard Actor Gary Cole FBI Special Agent Alden Parker Actor Grace Lynn Kung Doris Edwards Guest Star Ginifer King Lexi Davis Guest Star Patrick Y. Malone Chuck Gorton Guest Star Rio Mangini Ned Guest Star Scott Mosenson Harry Day Guest Star Anzu Lawson Sonia Bell Guest Star Don Swayze Pete Walker Guest Star Chuck Filipov Roy Smith Guest Star Chas. Floyd Johnson Executive Producer Mark Horowitz Executive Producer Frank Cardea Executive Producer George Schenck Executive Producer Steven D. Binder Executive Producer Scott Williams Executive Producer, Writer Donald P. Bellisario Executive Producer Margaret Rose Lester Writer