Shortly thereafter, he began receiving formal Brazilian Jiu-Jitsu instruction under Cassio Werneck, then training for three years under BJ Penn, before ultimately joining with Team Lloyd Irvin.

[36] On February 28, 2012, Keenan won the Abu Dhabi World Pro Trials Montreal Purple belt +74 kg absolute division.

[43] On December 8, 2013, Keenan won the medium-heavy/heavyweight division of the 2nd IBJJF Pro League for the prize of $5,000 by defeating Diego Gamoral and Jackson Souza.

[45] In April 2014 Keenan competed in the 2014 Abu Dhabi BJJ World Pro Championship, winning bronze in the black belt adult 94 kg division.

Cornelius famously competed in a submission-only, no time-limit match against Gordon Ryan on August 13, 2016 and was submitted with a heel hook after around 90 minutes.

[48] In 2021, Cornelius was unable to compete and was forced to withdraw from a match against Haisam Rida on Who's Number One[49] as a result of an aggravation of an old back injury suffered when deadlifting.

[52][53] Since launching the Legion AJJ academy, Keenan Cornelius has attracted some of ATOS' top athletes to his team including Andris Brunovskis and Darin Conner DeAngelis.

He and others have continued to iterate and invent techniques exploiting the lapels of the Gi jacket, a trend that is credited to Keenan's initial success with Worm Guard.