NCIS Bombshell: The Surprising Story Behind Mark Harmon’s Son Not Playing Young Gibbs in Origins

Sean Harmon played young Leroy Jethro Gibbs in several NCIS flashbacks, but he didn’t return for the prequel NCIS: Origins. Instead, Austin Stowell was cast in the role.

Although Sean isn’t acting in the series, he remains heavily involved as an executive producer alongside his father, Mark Harmon, who also narrates the show.

According to an October 15 In Touch report, Sean’s choice not to reprise the role created “some drama” behind the scenes. A source said Sean stepped back because he “has a lot on his plate.” However, the insider also claimed CBS wanted a more recognizable actor, and Mark agreed that choosing Stowell-who they felt had “leading man good looks and star power”-would help grow the franchise.

Mark told Forbes in October 2024 that the idea for Origins came from Sean, adding that he’s only involved in a supportive way. Sean explained that while playing young Gibbs was an honor, he never intended to build a career around the role. Moving into executive producing felt like the right next step.

Sean also endorsed Stowell as the perfect choice: “When he walked into the audition room, you could feel his talent and professionalism.”

Mark echoed that Sean simply has many interests-acting, writing, producing, surfing-and chose to focus on what he enjoys most.