Mark Harmon admitted he uses one of Gibbs' rules in his everyday life, but before anyone goes wild thinking about which ones would possibly factor into his real life, it's #9. During what I assumed would be a throwaway interview moment, I was impressed to see him answer a burning NCIS question with zero hesitation, addressing how the notion to "always carry a knife" has served him well.
Harmon was a guest recently on the NCIS podcast Partners & Probies, where co-host and Jimmy actor Brian Dietzen asked the former lead if he followed any of Gibbs famous rules in his everyday life. Here's what Harmon said as he started reaching for his pockets:
Nine. Number nine. Yeah. 'Carry a knife' is a good one for you. It really is. And you'd be surprised how useful it is. People ask. All the boys, you know, they all carry a pocket knife, a little pocket knife. And you can forget this sometimes, and you're getting on an airplane, and then they take your little pocket knife, and it's gone, which has happened, too. But it's just a handy tool.
The actor went on to say that he never used it as a means of defending himself, clarifying it's a tool he uses and not something he carries for protection. That made me chuckle, considering the 2026 TV schedule gave us at least two examples in which Gibbs murdered someone in cold blood.
NCIS: Origins showed Gibbs' murder of the cartel leader responsible for the death of his wife and daughter, something the flagship show talked about for years. Then the Season 23 penultimate (available to stream with a Paramount+ subscription) heavily implied Gibbs took a break from his retirement to help Alden Parker bring Director Vance's killer to justice.
Mark Harmon is not Gibbs, but I love that elements from the character have made it into his everyday life. I also have to wonder just how many times he's been asked that question to have replied as quickly as he did. Check out the clip below:
In fairness, Harmon recently talked to NCIS: Origins star Austin Stowell about the rules, so maybe they were fresh in his mind. The actor actually confessed he does not have an encyclopedic knowledge of the rules outside of the knife one, so I guess that really resonated with him.
NCIS is finished with its latest season, but fans can watch plenty of old episodes over on Paramount+. There's no better place to learn all of Gibbs' rules, so maybe check it out whilst ordering a pocket knife online.
