Keith is introduced as Lucas' uncle and Karen's best friend. He is the one that tells Whitey that Lucas should be on the basketball team. He often hangs out at his garage or Karen's Cafe. He is asked by Lucas to play with in the "Father-Son" basketball game. When Karen decides go to Italy for a cooking class, Keith offers to take care of Lucas while she's gone. When he drops her of at the airport, they kiss. While Karen's gone, Lucas starts dating Brooke and he gets a tattoo, Keith is very disappointed in him. The night Karen returns, he's so nervous before picking her up so he drinks a beer. When he and Lucas are going to the airport to pick her up, they get hit by a car. Lucas sustains several injures, while Keith gets some minor injuries. Lucas survives. Karen asks Keith if he had been drinking before he drove Lucas, and he told her he did, and she gets mad at him. He pays for Lucas' medical bills. He puts up his garage for sale to pay for them. Dan comes up with a business proposition for him. At first, Keith refuses, but then rethinks it. He signs the contracts, and Dan makes some big changes at the garage. He proposes to Karen, but she turns him down. Heartbroken, he decides to leave Tree Hill, and Lucas wants to come with him. While still hurt from Karen's rejection, Keith also sleeps with Deb. The two are unfortunately caught in the act by a very visibly upset Dan.
Keith and Lucas both reside in Charleston, and Keith is about to start a teaching job at a garage. He then gets a phone call from Deb, saying Dan had a heart attack. Both Keith and Lucas go back to Tree Hill. Dan then asks Keith if he can watch the dealership while he is in the hospital. A woman comes to the shop, wanting to buy a car. They go on a test drive, and flirt a bit. She tells him that her name is Jules, and he sells her the car. They start dating and their relationship is going forward very fast. Keith becomes vice president at the dealership.Later on, Lucas finds out that Jules had made a deal with Dan to make Keith fall in love with her. Jules swears that she told Dan that she didn't want to do it any more and that she is in love with Keith for real. Keith and Jules get engaged. Before the wedding, Karen found out about Dan's arrangement and confronts Jules. During the wedding, Jules runs away and Lucas and Karen tell Keith about Jules and he gets really mad and leaves town. Dd
Keith returns to Tree Hill, reuniting with Lucas and Karen. He and Karen finally begin a relationship and plan to wed. During the shooting, Keith tries to convince Jimmy Edwards to drop his gun to no avail. As Jimmy tells him what he had wanted, Keith tries to tell him that everything will get better, but Jimmy refuses to believe so. Jimmy then tells him that he's sorry before shooting himself. Later, Dan shoots Keith as he believed Keith had attempted to murder him in the dealership fire.
At Nathan and Haley's wedding, Karen reveals that she is pregnant with Keith's child. Keith's death has a huge impact on everyone's life in the show. Jimmy Edwards was framed as the murderer of Keith and most of the crew saw Jimmy as a monster except for Mouth. Keith is a guardian angel to Lucas and sends him multiple messages on how Keith really died. Keith continues to guide Lucas when Lucas collapses after the state championship on the middle of the road because he didn't take his heart medicine, while he is out, he has dreams of Keith and him spending time together. Lucas suggests he should be a bad person but Keith shows him how life would be if Lucas actually was a bad person, meaning Peyton would die in the shooting because Lucas wouldn't save her which would lead to Brooke becoming depressed. Keith takes Lucas around to everyone and the last spot is the hallway where Keith died. Keith tells Lucas to "open his eyes," sooner or later, Lucas wakes up and on prom he goes back to the hallway and sees Dan. Dan tells him "Keith is dead, open your eyes." Lucas sees Abby Brown who saw the whole murder which he visits her and finds out the truth. Keith would occasionally visit Dan as a ghost until he turned himself in for murder. When Karen's heart fails during the delivery of her and Keith's baby, she sees Keith in a dream and he tells her he'll be waiting, but she needs to go back to take care of their daughter. Keith rests in peace after everyone finds out his true murderer is his own brother, Dan. Keith doesn't show up until season 9 when Dan has just died, Keith takes Dan to the other side and forgives him after the latter's death. Dan and Keith are last seen leaving the hospital and Dan tells Keith he knows where Keith is going but he didn't know where he was going but Keith tells Dan that he is his "plus one."
Dan Scott (Brother): Dan and Keith were bitter rivals since childhood, disagreeing on many things. Though their relationship was never good, Keith still seems to care about his younger brother. However, when Keith went into Tree Hill High School during a school shooting to find his surrogate son, Lucas, Dan murdered him, believing he was responsible for a murder attempt that was actually Dan's ex-wife, Deb.
Lucas Scott (Nephew): Keith had been the father figure in Lucas life since childhood, even offering to adopt him when he and Karen got engaged. Other then Karen, Lucas was the most torn up about Keith's death and went to great lengths to prove Dan guilty of killing him.
Lily Scott (Daughter): Though Keith died before Lily was born, he still seems to have a connection and influence on the young girl's life. Lily often dreams of Keith, though it's unsure whether she even knows what he looks like, though since Jamie had a picture of him, it's likely Lily does too.
- Keith was the first main character to be killed off.
- Keith is the only main character to not appear in Season 5, Season 6, Season 7 and Season 8.
- Keith is the only main character who met an original character, but never met a new character (such as Jamie, Julian, Chase, Rachel, Millicent, Alex, Clay, Chris and Quinn).
- Keith is the third and final former main character to appear in the ninth and final season. Lucas was the first and Deb was the second.