Undrafted, Burnett played primarily in the then-named East Coast Hockey League before signing as a free agent with the San Jose Sharks of the National Hockey League on June 2, 1998. Used solely as an enforcer, Burnett was largely a journeyman. In Burnett's minor league career, he amassed 2,562 penalty minutes for 13 different teams. In the 1999–2000 season, in only 58 games with the Kentucky Thoroughblades of the American Hockey League, he had 506 penalty minutes. After signing with the Mighty Ducks of Anaheim on July 25, 2003, Garrett made his NHL debut in the 2003–04 season. Burnett's first career NHL goal came against Brent Johnson of the Phoenix Coyotes on March 17, 2004. The enforcer played 39 games and registered 184 penalty minutes while scoring one goal and adding two assists. Burnett participated in 22 fights in his sole NHL season with the Mighty Ducks of Anaheim. His reputation for having a "face of stone" was solidified in his March 19, 2004 fight against San Jose's Scott Parker, who sustained a broken hand from fighting Burnett. Burnett signed an NHL one-way contract for the 2004–05 season plus a one-year option, but due to the 2004 NHL Lockout only played briefly as the player-assistant coach for the Danbury Trashers of the United Hockey League in 2004. Burnett became a free agent and was signed by the Dallas Stars for the 2005–06 season, in which he played for Dallas's minor league affiliates the Iowa Stars and Phoenix RoadRunners. His last game played was in the Quebec-based Ligue nord-américaine de hockey on December 17, 2006 playing for the Summum Chiefs. The league suspended him for throwing a net at an opposing player.
Burnett was assaulted in the early hours of December 26, 2006 inside and outside of a night club in North Delta, British Columbia. He was in a coma in a Vancouver hospital. According to family, he was on life support and in a coma for 3 weeks and doing much better, yet he was also recovering/rehabilitating and being treated regularly as an outpatient four years later. As of 2010, no charges had been laid in the incident. In December 2008, Burnett sued the Delta police department and corporation of Delta among others as well as the owners of the nightclub Cheers, and bouncers in relation to the 2006 incident.
