Mark Harmon to appear on premiere of “NCIS” prequel, “NCIS: Origins”

The protagonist of 19 seasons of "NCIS" returns to his character's origin story.

The NCIS-verse has expanded, and Mark Harmon is still along for the ride.

CBS announced in January that a sixth spinoff series of the long-running military-police procedural was on its way, and that the new show, called NCIS: Origins, would focus on a younger version of Harmon's protagonist, Special Agent Leroy Jethro Gibbs. We now know that Harmon, who narrated the original series, will also take on narrating duties for Origins, as well as briefly appear in the pilot episode.

NCIS: Origins co-showrunner David J. North revealed on a recent panel that he, Harmon, and co-showrunner Gina Monreal came to the decision jointly. Though Origins is "focusing on [narrator Harmon] telling the story of 1991," he hinted that "as far as Mark appearing again, we are open to anything."

Harmon appeared in 437 episodes of NCIS across 19 seasons. A Marine Corps scout sniper who's tapped to command a team for the Naval Criminal Investigative Service (NCIS), Harmon plays Gibbs with a single-minded focus and toughness that belies a sensitive heart.

Harmon left NCIS mid-season 19, explaining on The Kelly Clarkson Show in 2023: "For the longest time, I was just tired," he said. "Part of taking the job [was] being home — with a young family — not traveling as much doing movies. [But] the first day, we worked 22 hours. So I thought, 'That's not exactly what I thought this was going to be.' But we had a lot of days like that in the first four years."

Related: The 25 essential NCIS episodes

But Harmon couldn't entirely shake the character he'd played for almost two decades; he reprised his role on several episodes of the spinoff NCIS: New Orleans, and has returned for his character's origin story.

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Origins will see Harmon's Gibbs at the outset of his career, as a fresh-faced special agent at NCIS's Camp Pendleton office. He'll be led there by a character familiar to NCIS fans: Special Agent-in-Charge Mike Franks, played by Muse Watson on the anchor series for 12 seasons and on Origins by Kyle Schmid.

Related: NCIS seasons, ranked from worst to best

Harmon will executive produce the series as well, alongside his son Sean. The coveted role of young Gibbs recently went to Austin Stowell who has appeared in films like Whiplash and Bridge of Spies.

"We just knew when Austin came in that he was Gibbs,” Monreal recently told Entertainment Weekly. “He embodied it. His talent is limitless, his dedication to the role, studying Mark, studying the show — he has a similar leadership quality that Mark had on set that bleeds into Gibbs the character.”

NCIS: Origins premieres on Monday, Oct. 14, at 10 p.m. ET/PT, on CBS.

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