Why Did Mark Harmon Leave NCIS? All About His Departure From the Hit CBS Series 4 Years Ago

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.