After retiring from MMA competition Chris switched his focus back to grappling events and also entered and won the No-Gi Black Belt World Championships in 2013, 2014, and 2015.
Growing up, Brennan claims that he lived in at least 19 different homes and played baseball and soccer, but was ultimately more interested in individual sports such as bodybuilding, surfing, gymnastics, and motocross.
In his next fight, Brennan fought against future MFC Lightweight Champion Antonio McKee for the King of the Cage Middleweight Superfight Championship and won via knockout with a head kick.
On August 4, 2001, Brennan defeated Kevin Hogan via armbar submission to become the new King of the Cage Middleweight Champion and then in his next fight, successfully defended his title against Steve Berger.
Brennan went 0–2 in Shooto, losing a controversial decision to Takanori Gomi before he made his PRIDE debut on October 5, 2003, at Bushido 1 against Eiji Mitsuoka and won via kimura submission in the first round.