After going undefeated in his first three professional mixed martial arts fights, Johnson signed with King of the Cage and challenged Tony Lopez for his KOTC heavyweight championship on March 26, 2010, at KOTC: Legacy. Also being the KOTC light heavyweight champion, Lopez was undefeated his last sixteen fights, which marked Johnson's most experienced opponent at the time. Johnson recorded the upset, using his wrestling to defeat the much more experienced Lopez via unanimous decision and becoming the KOTC heavyweight champion in just only his fourth professional fight. Johnson made his first title defense against then prospect and future UFC light heavyweight championDaniel Cormier at KOTC: Imminent Danger on August 13, 2010. He lost the fight and KOTC heavyweight championship in the first round via rear-naked choke submission, resulting in his first professional loss. Johnson rebounded from his loss to Cormier by defeating Boban Simic via unanimous decision on November 13, 2010 at KOTC: Infusion.
In April 2011, it was announced that Johnson had signed with Bellator, with his promotional debut expected to take place at Bellator 41 on April 16 against Carlos Flores. Johnson, however, was later replaced by Rudy Aguilar due to unknown reasons. Johnson eventually made his promotional debut against current UFC competitor Derrick Lewis at Bellator 46 on June 25, 2011. He won the fight via unanimous decision.
ONE Championship
After being sidelined for nearly two years due to issues with his Bellator contract, Johnson signed with Singapore-based promotion ONE Championship and faced former UFC heavyweight championTim Sylvia at on May 31, 2013. The fight was contested at a catchweight of 271 lbs. after Sylvia missed weight. Johnson won the fight via TKO due to a doctor stoppage in the third round after an elbow by Johnson opened up a cut on Sylvia's forehead. Johnson next faced Chris Lokteff at on November 15, 2013. He lost the fight via split decision.
Independent promotions
Over a year later, on November 22, 2014, Johnson faced Robert Neal at V3 Fights: Neal vs. Johnson and won via TKO due to elbows in the very first round.
Return to Bellator
Johnson re-signed with Bellator and faced former Bellator heavyweight championAlexander Volkov at Bellator 136 on April 10, 2015. He won the fight via split decision. Johnson faced former professional boxer Raphael Butler at Bellator 148 on January 29, 2016. Johnson utilised his wrestling to take Butler down and wear him down, before the referee stopped the bout in favour of Johnson, late in the third round due to punches. Johnson faced Cheick Kongo at Bellator 161 on September 16, 2016. He lost via majority decision.
Johnson has three daughters. Johnson used to train at Evolution MMA in Miami, FL. A gym owned by Head Coach Dan Monteleone. Johnson currently trains at Nashville MMA in Nashville, TN
