Gibbs has worked at NCIS for nearly two decades. He joined NCIS (then the NIS) in 1992 as a Junior Agent. He was typically referred to by his boss, Mike Franks, as "Probie" or "Gunny", a reference to his military rank of Gunnery Sergeant, something that continues to this day. Gibbs rose through the ranks until he was put in charge of the Major Case Response Team. He is often referred to as "Boss" or other humorous variations thereof by the members of his team.
Gibbs serves as the main protagonist of the television show NCIS (formerly Navy NCIS) and is portrayed by Mark Harmon, who has been nominate twice for the People's Choice Awards for this role.
Gibbs can be very charming in an understated way, and he has a dry sense of humor. He is something of a gentleman, often being very decorous and restrained, such as when his last ex-wife, Stephanie, lashed out at him for questioning her boyfriend as a suspect on a case. He already knew that her boyfriend was having an affair with her friend, but did not throw it in her face in retaliation.
Gibbs has a love for children, and often goes out of his way to help and comfort them. Some instances are when he finished the tree-house for the son of a dead marine, giving a scout who found a dead body his NCIS hat, letting a girl under NCIS protection stay at his house, and using his woodworking skill and his father's help to make toys for kids at Christmas time.
Gibbs is very unforgiving of his colleague's mistakes and demands high quality work from his team as well as himself. He rarely accepts apologies for mistakes, and will headslap most of the members of his team whenever they become distracted from the current case with DiNozzo usually receiving most of the slaps. He has even been known to headslap himself when he falsified evidence in order to protect a Marine's career.
Gibbs's chief hobby is wood-working, and is famous to his team and colleagues for building boats by hand in his basement. He has made four boats, the first three being named after each of his ex-wives and burned after their completion and his divorce from the wife in question. The fourth was named the Kelly, after his deceased daughter, and was gifted to his goddaughter, Amira. After removing the fourth boat from his basement, Gibbs moved on to making wooden toys for orphans, which he donated for Christmas in 2009.
Gibbs is a chronic coffee-drinker, even having a rule concerning coffee. He is farsighted, and for a few years he refused to wear the corrective lenses that he needed to allow him to read things like fine print. Gibbs also displays an uncanny knowledge of his co-workers's activities. He will often walk into the squad-room when his team is engaging in a completely off-topic conversation. When he arrives, his team will switch over to conversing about the case, covering for their distraction, but Gibbs often follows up with a comment related to the off-topic conversation, indicating that he is aware of what they were discussing which leaves his team surprised. During his brief tenure as head of the team, Tony attempted to replicate this by "listening in" on the team's conversation with a cell phone and an open line. However, Gibbs also demonstrated his knowledge of the conversation without Tony's props.
Gibbs is so dedicated to his job he even created his own set of rules.
Rule #1: Never screw over your partner.
Rule #2: Always wear gloves at a crime scene.
Rule #3: Don't believe what you're told. Double check.
Rule #3: Never be unreachable.
Rule #4: The best way to keep a secret? Keep it to yourself. Second best? Tell one other person - if you must. There is no third best.
Rule #5: You don't waste good.
Rule #6: Never say you're sorry. It's a sign of weakness.
Rule #7: Always be specific when you lie.
Rule #8: Never take anything for granted.
Rule #9: Never go anywhere without a knife.
Rule #10: Never get personally involved in a case.
Rule #11: When the job is done, walk away.
Rule #12: Never date a co-worker.
Rule #13: Never, ever involve a lawyer.
Rule #14: Bend the Line, do not ever Break It
Rule #15: Always work as a team.
Rule #16: If someone thinks they have the upper hand, break it.
Rule #18: It's better to seek forgiveness than ask permission.
Rule #22: Never, ever bother Gibbs in interrogation.
Rule #23: Never mess with a Marine's coffee... if you want to live.
Rule #27: There are two ways to follow someone. First way, they never notice you. Second way, they only notice you.
Rule #35: Always watch the watchers.
Rule #36: If you feel like you are being played, you probably are.
Rule #38: Your case, your lead.
Rule #39: There is no such thing as coincidence.
Rule #39a There is no such thing as a small world
Rule #40: If it seems someone is out to get you, they are.
Rule #42: Never accept an apology from someone who just sucker punched you.
Rule #44: First things first, hide the women and children.
Rule #45: Clean up the mess that you make.
Rule #51: Sometimes - you're wrong.
Rule #62: Always give people space when they get off the elevator.
Rule #69: Never trust a woman who doesn't trust her man.