Chaisson’s father, Kelvin Chaisson, played linebacker at Baylor University. Kelvin Chaisson was shot and killed in 2014 at the age of 33 when K’Lavon was a sophomore in high school.

Chaisson was born and grew up in Houston, Texas and attended North Shore Senior High School. He quit playing football as a freshman in order to focus on basketball. He returned to football going into his junior season. He became an immediate starter at defensive end for the Mustangs, leading Texas high schoolers with 15.5 sacks along with 50 tackles, including 13 for loss, and forced three fumbles and helped lead North Shore to the Class 6A Division I state championship game and was named first-team All-State by the Associated Press. Chaisson was named the defensive MVP of the game after recording two sacks, four tackles for loss, a blocked kick and a forced fumble in the game and making a game-saving tackle at fourth and goal to preserve a 21–14 win over Westlake High School. As a senior, Chaisson was named the 21-6A District Defensive MVP as well as All-Midlands by Scout.com and was invited to play in the 2017 Under Armour All-America Game. In the game he recorded six tackles, five of which were for loss, and tied the game’s record with three sacks. Rated a five star recruit by Scout.com and four star by 247Sports, ESPN and Rivals, Chaisson committed to play college football at Louisiana State University over offers from Florida and Texas.

Chaisson was chosen to wear the No. 18 Jersey by the Tigers’ coaching staff going into his redshirt sophomore season. He finished the season with 60 tackles and led the team with 6.5 sacks, 13.5 tackles for loss, and six quarterback hurries along with two passes broken up and a forced fumble and was named first team All-SEC. Chaisson was named the Defensive MVP of the 2019 Peach Bowl after a six-tackle, two-sack performance against Oklahoma. Chaisson had two tackles in LSU’s 42–25 win over Clemson in the 2020 National Championship Game. On January 17, 2020, Chaisson announced that he would forgo his remaining two years of eligibility and enter the 2020 NFL Draft.

Chaisson was selected with the 20th pick in the 2020 NFL draft by the Jacksonville Jaguars. The Jaguars originally acquired the selection in an October 2019 trade with the Los Angeles Rams that sent cornerback Jalen Ramsey to the Rams.

Chaisson made his NFL debut on September 13, 2020 in the season opener against the Indianapolis Colts, making two tackles. In the following week’s game against the Tennessee Titans, Chaisson recorded his first career sack on Ryan Tannehill during the 33–30 loss.