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Mark Harmon may have left NCIS, but he’ll forever be synonymous with Supervisory Special Agent Leroy Jethro Gibbs.

Harmon brought Gibbs to life for nearly two decades. The character first appeared on the legal drama JAG in 2003 before CBS launched NCIS later that same year. After leading NCIS for 18 seasons, Harmon departed the series in 2021.

“Mark’s always been part of the show, Mark’s always going to be part of the show,” former CBS Entertainment President Kelly Kahl told Deadline in September 2021. “In terms of his on-air appearances, we’re just going to have to see how it plays out going forward.”

Gibbs returned to the franchise in the spinoff NCIS: Origins, which premiered in October 2024. Set in 1991, the series follows a younger version of Gibbs — portrayed by Austin Stowell — during his early years as a special agent.

Harmon narrates the series and also serves as an executive producer. He’ll also guest star in the first-ever NCIS and NCIS: Origins crossover event on Nov. 11.

So, why did Mark Harmon leave NCIS? Here’s everything to know about why the actor exited the hit CBS procedural.

Why did Mark Harmon leave NCIS? 

Harmon stepped away from NCIS in 2021, with Gibbs’ final appearance coming in season 19, episode 4. The actor said his decision to exit the military police procedural series came down to timing and a desire to give his character a fitting conclusion.

“What has always drawn me [to NCIS] is the character I play and to keep that fresh and to keep it challenging,” Harmon said in a special featurette on the season 19 DVD release, per Entertainment Tonight. “Plot-wise, this character has taken the path that it did. I thought it was honest and okay.”

What has Mark Harmon said about his NCIS departure? 

After stepping away from NCIS, Harmon reflected on his exit during a November 2023 appearance on The Kelly Clarkson Show.

He admitted that fatigue played a role, recalling, “I think for the longest time, I was just tired. The first day [on NCIS], 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.”

In a July 2024 interview with Parade, Harmon offered further insight, framing his exit as a matter of timing rather than a firm decision to leave.

“It wasn’t so much a decision to leave as it was maybe just the right timing to push away a little bit,” he said. “I was thrilled with the storyline they came up with and how they handled the character. And the show’s continued. I was always of the opinion that this show would carry on, no matter who left or who joined.”

What did the NCIS cast and crew say about Mark Harmon’s exit? 

During a September 2023 interview with The Hollywood Reporter, NCIS executive producer Charles Floyd Johnson praised Harmon for his dedication to the series while also highlighting the toll it took on him.

“Coming in at 6:30 a.m., five days a week, and being the major character that was the linchpin — that’s pretty tough, and he did it for 18 seasons,” Johnson said. “He had just gotten to the place where he was getting close to turning 70, and he wanted to spend time with [wife] Pam [Dawber] and his kids.”

He added, “So he was leading up to it. It started probably [with him dropping hints] around the 15th or 16th season. But he was so loyal to that crew and so supportive of the show. He was very proud of it, and he stayed on longer than he even intended.”

Sean Murray, who has played Special Agent Timothy McGee since 2003, reflected on filming Harmon’s final scene while speaking to Entertainment Weekly in February 2023.

“I had lots of feelings about it because, well, you know, it’s Harmon, who is like a mentor to me, and saying goodbye on screen was hard. But at the same time, I felt that if anyone were to do it, McGee is the right one,” he said.

How was Mark Harmon’s character written off in NCIS? 

Gibbs’ exit left the door open for possible returns to NCIS.

In season 19, episode 4, the character solved a high-profile case in Alaska and made the decision to remain there rather than return to Washington, D.C. Gibbs’ departure was framed as a natural next chapter in his life, allowing him to spend time away from the Bureau after decades of service.

“We were in the water doing the fly fishing, and as I’m saying goodbye to Mark, the whole crew is crying,” Murray recalled to Entertainment Weekly of his final scene with Harmon. “Danny, one of the grips, came up to me afterward, and he goes, ‘I got a bone to pick with you. I’m a grown man. You had me crying, standing in the river.’ “

What has Mark Harmon been up to since leaving NCIS? 

Since exiting NCIS in 2021, Harmon has continued to work, emphasizing in a 2023 PEOPLE interview that he “left the show, I didn’t retire.”

In November 2023, Harmon ventured into publishing with the release of Ghosts of Honolulu: A Japanese Spy, a Japanese American Spy Hunter, and the Untold Story of Pearl Harbor, co-written with former NCIS technical advisor Leon Carroll Jr. Harmon also reprised his role as Ryan Coleman opposite Jamie Lee Curtis in 2025’s Freakier Friday.

Harmon has remained connected to the NCIS universe through the prequel series NCIS: Origins, which debuted in October 2024. He serves as both narrator and executive producer for the show, which explores the younger years of Leroy Jethro Gibbs (Austin Stowell).

While Harmon primarily works behind the scenes these days, he’ll make a guest appearance in a highly-anticipated Nov. 11 crossover event between NCIS and NCIS: Origins. The official synopsis reads, “Younger Gibbs and team investigate the small-town death of a naval officer in the ‘90s on NCIS: Origins — a case that’s unexpectedly re-opened in the present day on NCIS.”

“They came to me with an idea for Gibbs that I liked, and it seemed like a good time to check in with him. I hope fans enjoy it,” Harmon said in an October 2025 statement.