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 David McCallum Dr. Donald "Ducky" Mallard Actor Gary Cole FBI Special Agent Alden Parker Actor Joe Spano Tobias "T.C." Fornell Guest Star Teri Polo Vivian Kolchak Guest Star Erik Passoja Wayne Sweeny Guest Star Vanessa Lachey Special Agent Jane Tennant Guest Star Jason Antoon Ernie Malick Guest Star Karina Noelle Castillo Agent Ramirez Guest Star Susan Ruttan Samantha "Sammy" Delfino Guest Star Eric Lynch Gary Shay Guest Star Michael Weston Herman Maxwell Guest Star Chas. Floyd Johnson Executive Producer Mark Horowitz Executive Producer Mark Harmon 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 Tawnia McKiernan Director