As "NCIS" continued, Gibbs kept adding to his list of rules. We know that he has nearly 100 of them, but unfortunately, even the most hardcore fan isn't going to be able to tell you all of them.

Leroy Jethro Gibbs (Mark Harmon) lived by his rules on NCIS. For 19 seasons, Gibbs spouted his guidance to his team of special agents, giving them a handbook to live and work by.

During NCIS Season 18 episode 16 (titled “Rule 91”), Gibbs is talking to Marcie Warren (), the reporter who wrote about his brush with the law after beating up a suspect.When she sees his boat ...

While Mark Harmon's Gibbs is no longer part of the "NCIS" family he had a surprising effect on the show's crossover with spin-off "NCIS Hawai'i".

Gibbs' Rules are a part of NCIS, but Origins star Austin Stowell reveals the real-life rule he learned from "sage" Mark Harmon on the set of the prequel. Skip to main content.