Early career

McKenzie began his professional mixed martial arts career with a TKO victory over Brett Held in British Columbia, Canada. This was his only fight to go to a second round in his career prior to the UFC. Less than a month later, McKenzie faced Abe Jones, defeating him via triangle choke in the first round.^[8]

After taking almost a year away from competition, McKenzie returned to face Benny Mawson, once again in British Columbia, Canada. After 100 seconds, McKenzie caught his opponent in a guillotine choke, taking his record to 3–0.^[8] This began his long stretch of victories via guillotine choke. During this near-record setting span, McKenzie fought several times in B.C. and in various locations in Washington. McKenzie also fought in Bahrain on one occasion, taking just four minutes to defeat his opponent with a guillotine choke. Before signing with the UFC, McKenzie had a record of 11–0, with nine successive first-round guillotine choke finishes.^[8]

The Ultimate Fighter

McKenzie signed with the Ultimate Fighting Championship to appear on The Ultimate Fighter: Team GSP vs. Team Koscheck.^[4]

McKenzie competed on the debut episode against Amir Khillah, to get into the house. Prior to the fight, Georges St-Pierre predicted a guillotine choke submission victory for McKenzie. This proved to be correct as McKenzie forced a technical submission victory over Khillah in the opening round.^[9]

In the second episode, the team picks were made. Georges St-Pierre picked McKenzie as his sixth pick (twelfth overall).^[10]

McKenzie was next picked to face Koscheck's number one pick Marc Stevens. Stevens went for an early takedown, but was caught in a guillotine choke submission. With just 18 seconds^[11][12] on the clock, Stevens passed out and McKenzie was declared the winner.^[13]

In the quarterfinals, McKenzie faced Nam Phan of Team Koscheck. He lost the fight via TKO in the second round after Phan dropped him with a combo to the body.^[14]

Ultimate Fighting Championship

McKenzie made his UFC debut at The Ultimate Fighter: Team GSP vs. Team Koscheck Finale against Aaron Wilkinson. He went on to defeat Wilkinson via submission (a guillotine choke applied to Wilkinson's jaw) at 2:03 of round one. McKenzie earned the Submission of the Night award for his performance.

McKenzie made a quick return to the octagon as he replaced Melvin Guillard to face Yves Edwards at UFC: Fight for the Troops 2 on January 22, 2011.^[15] After a back and forth battle that saw both men in control, McKenzie lost the fight via rear naked choke submission in the second round.

McKenzie was expected to face Bart Palaszewski on May 28, 2011, at UFC 130,^[16] but was forced off the card with an injury and was replaced by Gleison Tibau.^[17]

McKenzie faced Vagner Rocha on September 17, 2011, at UFC Fight Night 25. He lost the fight via submission in the second round.^[18]

McKenzie was expected to face Michael Johnson on January 28, 2012, at UFC on Fox 2. However, McKenzie was forced out of the bout with an injury and was replaced by Shane Roller.^[19]

McKenzie was expected to face Aaron Riley on May 15, 2012, at UFC on Fuel TV: The Korean Zombie vs. Poirier.^[20] However, Riley was pulled from the event and replaced by promotional newcomer Marcus LeVesseur.^[21] McKenzie won the fight via submission in the first round.

McKenzie dropped to featherweight and faced Chad Mendes on July 7, 2012, at UFC 148. He lost the fight via first-round TKO.^[22]

McKenzie was expected to face Leonard Garcia on December 29, 2012, at UFC 155.^[23] However, McKenzie pulled out of the bout, citing an injury, and was replaced by Max Holloway.^[24]

The bout with Leonard Garcia was rescheduled for April 27, 2013, at UFC 159.^[25] McKenzie won the fight via unanimous decision, the first decision win of his career.

McKenzie faced Sam Stout in a lightweight bout on December 14, 2013, at UFC on Fox 9.^[26] He lost the fight via unanimous decision. During the fight, McKenzie wore basketball shorts with the tag still on them, which UFC president Dana White called "UFC amateur hour."^[27] McKenzie was subsequently released from the promotion.^[28]

Post-UFC

McKenzie fought at a 180-pound catchweight on April 12, 2014, against Mark Dobie at Battle for the Border 3.^[29] He won the fight via rear-naked choke submission.^[30]

On October 3, 2014, McKenzie faced Brock Larson in the opening round of the BattleGrounds MMA one-night welterweight tournament. He lost the fight via second-round submission.^[31]

On December 18, 2014, McKenzie announced his retirement from mixed martial arts.^[32]

Two months after announcing his first retirement, it was announced on February 3, 2015, that McKenzie had signed with WSOF. He faced Andrew McInnes at World Series of Fighting 18: Moraes vs. Hill on February 12, 2015.^[33] He lost the fight via disqualification, after a headbutt from McKenzie rendered McInnes unable to continue.

On October 14, 2017, McKenzie fought for Venator, losing by first-round TKO to Stefano Paterno. He was later suspended by the Italian MMA commission for refusing to provide a sample to anti-doping officers.^[34]

The following year in September 2018, McKenzie was due to face J.D. Domengeaux at a Tuff-N-Uff event. The fight was called off the day before the bout after McKenzie refused to provide a urine sample to anti-doping and then attempted to provide fake urine. In November Mckenzie was suspended by the Nevada Athletic Commission for four years.^[35]