| Character name | Actor | Job | Character status |
|---|
| Leroy Jethro Gibbs | Mark Harmon | Special Agent In Charge // Major Case Response Team Supervisory Agent, NCIS (Retires from NCIS and moved to Alaska in season 19) | Regular (Season 1-19) |
| Anthony DiNozzo | Michael Weatherly | Special Agent // Major Case Response Team Senior Field Agent, NCIS
(Resigned from NCIS and moved to Paris at the end of season 13) | Regular (Season 1-13) |
| Ziva David | Cote de Pablo | Special Agent // Major Case Response Team Probationary Field Agent, NCIS
Former Mossad officer.
(Resigned from NCIS in ") | Regular (Season 3–11) Guest (Season 16) Recurring (Season 17) |
| Abby Sciuto | Pauley Perrette | Forensic Specialist, NCIS (Left the agency to start a charity in England) | Regular (Season 1-15) |
| Timothy McGee | Sean Murray | Special Agent // Major Case Response Team Junior Field Agent, NCIS | Regular (Season 2–present)
Recurring (Season 1) |
| Dr.
Donald "Ducky" Mallard | David McCal
|