Mark Harmon will appear in every episode of NCIS: Origins Season 3, CBS has confirmed. Harmon returns as the elder version of Leroy Jethro Gibbs, the character he played for more than 18 seasons on the main NCIS series. His season-long arc centers on a present-day mystery tied to Gibbs’s time at Camp Pendleton in the 1990s.
His on-screen appearances in the prequel have been limited until now. Harmon showed up in the NCIS: Origins series premiere and during the November 2025 crossover event with the main NCIS series, but has otherwise stayed behind the camera in his role as executive producer and narrator. Season 3 changes that arrangement, with his presence extending through the full episode order rather than being held back for event installments.
Mark Harmon’s role in NCIS: Origins
Austin Stowell plays the younger Gibbs throughout the prequel, set during his 1990s service at Camp Pendleton. Harmon’s elder Gibbs frames the series, narrating over the past-timeline action from a present-day vantage point. That format has let the production keep Harmon connected to the NCIS franchise without revising the exit his character made from the main show. Until Season 3, the narration largely kept him off screen.
His NCIS run lasted more than 18 seasons, making Gibbs one of the longest-serving characters in network procedural history. The departure came in Season 19, when Gibbs chose to stay in a remote part of Alaska rather than return to the Naval Criminal Investigative Service. That decision held. NCIS: Origins has built around it rather than undoing it, and Season 3 extends that approach by giving Harmon a season-long storyline that looks back rather than forward.
Season 2 finale recap
NCIS: Origins Season 2 closed on two unresolved threads. Young Gibbs and Lala (Mariel Molino) kissed for the first time in the finale, capping a slow-burn dynamic that had developed across both seasons of the prequel. Randy (Caleb Foote) was also kidnapped after uncovering something sensitive while digitizing team files, with his fate left open when the episode ended.
CBS has not confirmed how Harmon’s expanded arc connects to either of those threads. His Season 3 storyline runs through the Camp Pendleton era, which is the same period the younger Gibbs occupies during the prequel timeline. The specifics have not been disclosed ahead of the fall premiere.
When NCIS: Origins season 3 airs
Season 3 marks the prequel’s third run. It returns this fall on CBS, airing Tuesdays at 10/9c, with episodes streaming on Paramount+ the same night. Executive producers for the season include Harmon alongside David J. North, Sean Harmon, Michele Greco, and Eric Christian Olsen. No specific premiere date has been announced.