Mark Harmon plays Special Agent Leroy Jethro Gibbs on "NCIS." He first appeared as this character on the CBS television show "JAG" for two episodes in 2003. "NCIS," which debuted in 2003 as "Navy NCIS: Naval Criminal Investigative Service," is a spin-off of "JAG." "NCIS" became a hit show, and as of 2016, it remains on the air.
"NCIS" is a military crime procedural television show. Harmon's character is a former U.S. Marine Corps gunnery sergeant and sniper who now leads a team of Navy Criminal Investigative Service agents. This team investigates crimes that involve members of the Navy and Marine Corps. Gibbs is a stoic character, who is an effective leader as well as a father figure to some NCIS team members.
In 2007, friction developed between Harmon and Don Bellisario, a creator and producer of "NCIS," over the management of the show. Bellisario left the program. In 2008, Harmon became a producer on "NCIS."
Harmon received the role following a successful four-episode stint on "The West Wing," in which he played a Secret Service agent. Critics have praised him for his role as Gibbs, and he has received three People's Choice Award nominations for his work. Harmon's son, Sean, has portrayed a younger Gibbs in flashbacks.