NCIS is a television show that follows a fictional team of the Naval Criminal Investigative Service Major Case Response Team special agents, headquartered at the Washington Navy Yard in Washington, D.C.. It is described by the actors and producers as being distinguished by its comedy elements, ensemble acting and character-driven plots.

As NCIS is a federal law enforcement agency with jurisdiction on crimes involving persons and property associated with the U.S. Navy and the U.S. Marine Corps, the team is frequently assigned to high-profile cases such as the death of the President's nuclear missile aide, a bomb situation on a U.S. Navy warship, the death of a celebrity on a reality show set on a USMC base, terrorist threats, and kidnappings. In a number of episodes on NCIS, Mark Harmon's character, Gibbs is seen wearing an old shirt with NIS written on it. This is not a mistake, as Navy veterans will often point out. Prior to it becoming NCIS, it was the Naval Investigative Service (NIS). This also effectively plays into the idea that Gibbs has been with NCIS for quite some time longer than the others.