Sean Harmon, the actor who first played the younger version of his father Mark Harmon's Leroy Jethro Gibbs, returned to the NCIS franchise on Tuesday, October 13, 2026, in a new role on CBS's prequel series NCIS: Origins. According to CBR, Sean Harmon appears in Season 3, Episode 2, titled My Own Worst Enemy, playing FBI Agent Casey Bloom rather than reprising his old part as young Gibbs.
The episode marks the actor's first on-screen appearance in the franchise since NCIS Season 18 in 2021, when he played young Gibbs one year before Mark Harmon exited the flagship series. For Iowa viewers who have followed the NCIS franchise for two decades, the return of a Harmon family member to the screen is a familiar piece of television history coming full circle.
Who Is Sean Harmon Playing in NCIS: Origins?
Per CBR's report, Sean Harmon plays Casey Bloom, a senior FBI agent who is the partner of Agent Josephine Swanson, played by Hannah Barefoot. Bloom steps in to lead the FBI's murder investigation into Woodrow Woody Browne, played by Bobby Moynihan, after Swanson gets pulled into another case.
Bloom arrives with a reputation. Randy Randolf suggests the character was the inspiration for Keanu Reeves' iconic FBI agent Johnny Utah in the 1991 film Point Break. Bloom does not exactly deny it, telling Mike Franks, played by Kyle Schmid, that he likes to think there's a little Keanu in all of us.
The character also explains his unfamiliarity with the early 1990s setting: he has spent the past year undercover with a biker gang, and he describes the bikers as beautiful people who are just carrying a lot of pain. Franks, who has developed a crush on Swanson, is visibly disappointed that Bloom showed up instead of her.
Why Sean Harmon Did Not Return as Young Gibbs
Austin Stowell has played the young Gibbs in NCIS: Origins since the prequel launched on October 14, 2024. Sean Harmon, who co-created the concept for the prequel and serves as an executive producer alongside his father, chose to step back from acting in the role to focus on producing, according to CBR.
Some fans initially criticized Stowell for not resembling Mark Harmon, but audiences have largely accepted the recasting as the first two seasons built out their own version of the character. Seeing the two actors who have both played young Gibbs appear in the same episode also helps cement Stowell's ownership of the part.
Sean Harmon's version of Gibbs was the original replacement for the character in flashback scenes on the flagship series, appearing most notably in NCIS Season 18, Episode 2, alongside Adam Campbell's young Ducky. His new role as Bloom expands the prequel's roster of FBI agents, which already includes Swanson and a younger version of Joe Spano's Tobias Fornell.
Mark Harmon Also Returns to the NCIS Universe
The Harmon family involvement does not stop with Sean. USA Today reports that NCIS: Origins reunites Mark Harmon's Gibbs with Michael Weatherly's DiNozzo, who is now the agency's director. In the story, Gibbs returns to NCIS headquarters in Washington, D.C., to seek help after being shot by unknown assailants.
Story News also reported that CBS released a photo of Mark Harmon as Gibbs alongside Moynihan's Woody ahead of the Season 3, Episode 2 broadcast, and confirmed Sean Harmon's guest-starring role.
People magazine published an exclusive clip showing Mark Harmon's Gibbs making a long-awaited return to society and meeting with an old friend, part of the same promotional rollout for the episode.
What Comes Next for Agent Bloom
According to CBR, the prequel appears to have more plans for the character. NCIS Special Agent-in-Charge Cliff Wheeler, played by Patrick Fischler, tells Bloom during the episode that NCIS will see him again, signaling that Sean Harmon's return may not be a one-off guest spot.
The episode, created by Gina Lucita Monreal and David J. North and written by Brendan Fehily, aired under the TV-14 rating on CBS, which remains one of the few broadcast networks still investing heavily in scripted crime dramas with broad family appeal.
Frequently Asked Questions
Who did Sean Harmon play before Casey Bloom?
Sean Harmon played the younger version of his father Mark Harmon's character, Leroy Jethro Gibbs, in flashback scenes on the original NCIS series, most recently in Season 18, Episode 2, which aired in 2021.
Why was Austin Stowell cast as young Gibbs instead?
Sean Harmon wanted to focus on his work as an executive producer of NCIS: Origins, so Austin Stowell took over the role of young Gibbs when the prequel launched in October 2024.
When did Sean Harmon's NCIS: Origins episode air?
The episode, Season 3, Episode 2, titled My Own Worst Enemy, aired on CBS on Tuesday, October 13, 2026.