Mark Harmon Shares the Most Valuable Lesson He Learned from His Late Dad

After portraying NCIS lead investigator Leroy Jethro Gibbs for nearly two decades, Mark Harmon has become almost inseparable from his iconic character in the minds of fans. It’s no surprise, then, that the advice the 67-year-old actor shares in a new People interview feels like it could have been lifted straight from Gibbs’ legendary rulebook-or even a heartfelt conversation with Gibbs’ father, played by Ralph Waite. And that’s high praise.

Harmon opened up about lessons from his own late father, Tom, who passed away when Harmon was 38. “My dad taught me, if it’s not true, don’t worry about it,” he shared. Another piece of wisdom: “Work your (rear) off, and don’t let the effort show.”

But it wasn’t all about hard work. Harmon also learned the importance of treating everyone with respect. “Treat people the same, not based on who they are or what they are. Show them common kindness. Don’t be colored by their fame or profession,” he said.

True to Gibbs’ no-nonsense style, Harmon added, “I don’t get all excited by people blowing smoke up my (rear). You have to stay honest.”

For longtime NCIS fans, there may even be room for a new Gibbs rule: after all, Harmon recently broke one of Gibbs’ own commandments, tearing up the rule advising investigators never to get personally involved in a case.

Whether it’s on screen or off, Mark Harmon continues to live by principles that would make Gibbs proud.