NCIS is an American police procedural television series, revolving around a fictional team of special agents from the Naval Criminal Investigative Service, which investigates crimes involving the U.S. Navy and Marine Corps. The series was created by Donald P. Bellisario and Don McGill as a backdoor pilot with the season eight episodes "Ice Queen" and "Meltdown" of JAG. The series premiered on September 23, 2003, featuring an ensemble cast, which has included: Mark Harmon, Sasha Alexander, Michael Weatherly, Pauley Perrette, David McCallum, Sean Murray, Cote de Pablo, Lauren Holly, Rocky Carroll, Brian Dietzen, Emily Wickersham, Wilmer Valderrama, Jennifer Esposito, Duane Henry, Maria Bello, Diona Reasonover, Katrina Law, and Gary Cole.
Overview Main characters +Key scope="row" Recurring scope="row" Guest Character Actor Season 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Leroy Jethro Gibbs Mark Harmon colspan="19" colspan="5" Caitlin "Kate" Todd Sasha Alexander colspan="2" colspan="4" colspan="2" colspan="2" colspan="12" Anthony "Tony" DiNozzo Jr. Michael Weatherly colspan="13" colspan="7" colspan="2" colspan="1" Abigail "Abby" Sciuto Pauley Perrette colspan="15" colspan="9" Dr. Donald "Ducky" Mallard David McCallum colspan="20" colspan="4" Timothy "Tim" McGee Sean Murray colspan="23" Ziva David Cote de Pablo colspan="2" colspan="9" colspan="4" colspan="7" Jenny Shepard Lauren Holly colspan="2" colspan="3" colspan="2" colspan="2" colspan="2" colspan="12" Leon Vance Rocky Carroll colspan="4" colspan="18" colspan="1" Dr. James "Jimmy" Palmer Brian Dietzen colspan="9" colspan="15" Eleanor "Ellie" Bishop Emily Wickersham colspan="10" colspan="8" colspan="4" colspan="1" Nicholas "Nick" Torres Wilmer Valderrama colspan="13" colspan="11" Alexandra "Alex" Quinn Jennifer Esposito colspan="13" colspan="10" Clayton Reeves Duane Henry colspan="12" colspan="2" colspan="9" Dr. Jacqueline "Jack" Sloane Maria Bello colspan="14" colspan="4" colspan="6" Kasie Hines Diona Reasonover colspan="14" colspan="9" Jessica "Jess" Knight Katrina Law colspan="17" colspan="6" Alden Parker Gary Cole colspan="18" colspan="6"
Table notes
Character Actor Rank/position Seasons First episode Last episode No. ofepisodes (credited) Notes Regular Recurring Guest Leroy Jethro Gibbs Mark Harmon NCIS Supervisory Special Agent / Marine Gunnery Sergeant 1–19 "Yankee White" (1.01) "Great Wide Open" (19.04) 435 Caitlin "Kate" Todd Sasha Alexander NCIS Special Agent / Secret Service Special Agent 1–2 3, 8–9, 12 "The Lost Boys" (12.23) 51 Anthony "Tony" DiNozzo Michael Weatherly Senior Special Agent / Baltimore PD Detective / Director 1–13, 24– 21 308 Abigail "Abby" Sciuto Pauley Perrette Forensic Specialist 1–15 "Two Steps Back" (15.22) 354 Dr. Donald "Ducky" Mallard David McCallum Chief Medical Examiner / Profiler / Historian / RAMC Doctor 1–21 "Black Sky" (20.22) 460 Ducky Mallard was Medical Examiner during seasons 1–16.David McCallum is credited with the 'and' billing in seasons 1–18 and is credited with the 'with' (sharing with Rocky Carroll) billing in seasons 19–21. He remains in the opening credits for the first two episodes in Season 21 despite McCallum's death in September 2023, five months before Season 21 premiered and two months before that season began filming. Timothy "Tim" McGee Sean Murray Senior Special Agent 2– 1 "Sub Rosa" (1.07) 492 Timothy McGee was a Special Agent during Seasons 2–13. Ziva David Cote de Pablo NCIS Special Agent / Mossad Officer 3–11 17 3, 16 "Kill Ari (Part I)" (3.01) "In the Wind" (17.11) 194 Ziva David was a Mossad Officer during Seasons 3–6. Jenny Shepard Lauren Holly NCIS Director / NCIS Special Agent 3–5 3 9, 12 "The Lost Boys" (12.23) 65 Leon Vance Rocky Carroll NCIS Director / NCIS Assistant Director / NCIS Special Agent 6–23 5 "Internal Affairs" (5.14) "All Good Things" (23.13) 399 Leon Vance was Assistant Director during season 5.Rocky Carroll is credited with the 'with' billing. Dr. James "Jimmy" Palmer Brian Dietzen Chief Medical Examiner 10– 1–9 "Split Decision" (1.21) 407 Jimmy Palmer was Assistant Medical Examiner during seasons 1–14. Eleanor "Ellie" Bishop Emily Wickersham NCIS Special Agent / NSA Analyst 11–18 11 23 "Gut Check" (11.09) "Her" (23.10) 174 Nicholas "Nick" Torres Wilmer Valderrama NCIS Special Agent 14– "Rogue" (14.01) 202 Alexandra "Alex" Quinn Jennifer Esposito NCIS Special Agent / NCIS FLETC Trainer 14 "Rendezvous" (14.24) 24 Clayton Reeves Duane Henry MI6 Officer / NCIS-MI6 Liaison 14–15 13 "Dead Letter" (13.23) "Two Steps Back" (15.22) 47 Dr. Jacqueline "Jack" Sloane Maria Bello Psychologist / NCIS Special Agent 15–18 15 "Skeleton Crew" (15.04) "True Believer" (18.08) 73 Kasie Hines Diona Reasonover Forensic Scientist 16– 15 "One Man's Trash" (15.17) 157 Jessica Knight Katrina Law NCIS Special Agent / NCIS React Team Leader 19– 18 "Blown Away" (18.15) 96 Alden Parker Gary Cole NCIS Supervisory Special Agent / FBI Special Agent 19 "Nearly Departed" (19.02) 93 Gary Cole is credited with the 'and' billing
Notable recurring and guest characters +Key scope="row" Recurring scope="row" Guest