There was no word on the cause of Slice's death.
Slice had been hospitalized Monday for undisclosed reasons near his home in South Florida, according to Coral Springs police, who had been dispatched to his residence to prevent a potential gathering outside. They said no foul play was suspected.
Slice, birth name Kevin Ferguson, was a former backyard brawler and Internet sensation. He was born in the Bahamas in 1974 but made his home in the Miami area.
He was signed to Bellator MMA and scheduled to headline Bellator 158 on July 16 in London against James Thompson.
He last fought at Bellator 149 on Feb. 19 in Houston. Slice (5-2) defeated Dhafir Harris, aka Dada5000, in a three-round decision. The result was later changed to a no-contest by the Texas commission, after Slice tested positive for anabolic steroids and an elevated testosterone ratio.