NCIS : Los Angeles - Season 3 (Updated Episode 12)

The show was known as NCIS: Legend while in production (referring to the episodes of NCIS in which the spin-off was introduced), and other names considered included NCIS: OSP (Office of Special Projects) and NCIS: Undercover.[10] Filming started in February 2009, with the characters being introduced in the two-part NCIS episode titled "Legend", the first part of which aired on April 28, 2009.[10][18] This episode served as a backdoor pilot for the series, in a manner similar to the introduction of NCIS, which was introduced by way of a two-part episode of JAG.

Chris O'Donnell plays the lead character, G. Callen, a lead agent whose natural talent for undercover work is legendary.[19] LL Cool J plays the role of Special Agent Sam Hanna, a former Navy SEAL, who is fluent in Arabic and an expert on Middle Eastern culture.[9] Daniela Ruah plays an agent named Kensi Blye. Adam Jamal Craig playing rookie field agent Dominic Vail was credited as a regular through the first dozen episodes of season one, but was subsequently written out of the show,[20] and the character was killed off in episode 21. Eric Christian Olsen plays Marty Deeks, the team's liaison with the Los Angeles Police Department. Olsen appears in two episodes of the first season as a guest star, and joins the cast full time in season two as Craig/Vail's replacement.

Peter Cambor plays Nate Getz, the team's operational psychologist, who supports their missions through surveillance and profiling of targets and ongoing monitoring of the OSP team members' mental health. Cambor was listed as a main cast member throughout the first season, but was downgraded to recurring status at the start of season 2 appearing in four second season episodes to-date: the first, third, fourteenth, and eighteenth episodes.

The cast is rounded out by Linda Hunt playing the OSP's operations manager Hetty Lange, a former agent with a mysterious past, and Barrett Foa as Eric Beale, the team's technical analyst and resident geek.