NCIS’s Mark Harmon Reveals His Favorite Gibbs Rule & It’s Surprisingly Practical

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Leroy Jethro Gibbs, the character from the TV show NCIS, was known for his many rules. Mark Harmon, the actor who portrayed him, recently shared which one was his personal favorite.

Mark Harmon first appeared as Leroy Jethro Gibbs in a two-part episode of JAG called “Ice Queen” and “Meltdown.” He then played Gibbs on NCIS for the show’s first 18 seasons, plus the first four episodes of Season 19—nearly 20 years in total. Throughout that time, fans of the CBS drama learned about the many personal rules Gibbs lived by. Harmon says the rule he finds most valuable is also the most useful in everyday life.

Mark Harmon recently joined the Partners & Probies podcast with Leon Carroll Jr., a technical advisor for NCIS and former special agent, to discuss their new book, Ghosts of Sicily. While on the show, hosted by NCIS stars Brian Dietzen and Diona Reasonover, Harmon answered a fan question about his favorite Gibbs rule in a memorable way – by taking out a pocket knife and revealing his choice.

It’s smart to carry a knife – you’d be surprised how often it comes in handy. Most boys have a small pocket knife, and it’s easy to forget about until you’re at the airport and have to give it up. That’s happened to me before. It’s just a useful tool, and I’m not talking about self-defense, but people frequently ask if anyone has a knife available.

Over the many seasons of NCIS on CBS, viewers have learned about numerous “Gibbs Rules.” One of the most practical? Always carry a pocketknife. As Agent Gibbs explained, it can be helpful either for yourself or to lend to someone in need. And it’s not just the blade – the small scissors often included are useful too.

Mark Harmon, who played Gibbs, often used knives on NCIS for more than just simple tasks like cutting rope or wood. His character, a former Marine and NCIS Special Agent, sometimes used blades to cut tires or in actual fights. Because of this background, carrying a knife was particularly important for Gibbs – more so than for most people.

These days, Gibbs is enjoying a much more peaceful life. After retiring from NCIS during season 18, his character chose to stay in Naktok Bay, Alaska, following a final mission with Timothy McGee and Alden Parker, as seen in the episode “Great Wide Open.” Even though he’s living in a remote location now, he still likes to keep a knife handy for safety.

Mark Harmon hasn’t returned as Gibbs on the original NCIS since leaving in 2021, but he continues to portray the character in the prequel series, NCIS: Origins. He both executive produces and narrates Origins as the older version of Gibbs, while Austin Stowell plays the younger Gibbs. Harmon has also made two on-screen appearances as Gibbs in NCIS: Origins – once in the pilot episode, and again in the season two episode, “Funny How Time Slips Away.”

Season 3 of NCIS: Origins is scheduled to premiere on CBS in the 2026-2027 television season, but it will have fewer episodes than seasons 1 and 2. Hopefully, one of the ten new episodes will finally explain why Gibbs always carried a knife in the original NCIS series.

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2026-05-06 05:31