Patricio "Pitbull" Freire made his MMA debut while still a teenager, at only 17 years old.  He won his first bout via TKO in the first round and never looked back.  Freire has a black belt in Brazilian Jiu-Jitsu and trains with Team Nogueira.  After dismantling the local Brazilian MMA circuit, going undefeated at 12-0 and finishing all but two fights, Bellator Fighting Championships signed him to compete in their next season's tournament. 

Freire's Bellator FC debut came at Bellator 15, where he quickly submitted William Romero via heel hook in round one.  He would go on to reach the finals, but ultimately lose a very close split decision in the finals to Joe Warren at Bellator 23. Pitbull, as many call him, joined the season 4 tournament and would go on to finish every fight leading up to the finals and ultimately win a decision over Daniel Straus to claim the tournament championship and the right to challenge Joe Warren for his Championship belt. 

 
Training for his title shot, Freire broke his hand and had to pull out of the fight.  Pat Curran would go on to face Joe Warren and take the belt from Warren via KO.  Freire was then scheduled to fight Curran for the title, but the injury bug would hit again, this time for his opponent who suffered a broken orbital bone. Patricio is now slated to finally get his title shot at Bellator 85 against Curran. When they fight, it will have been just under twenty two months since he last fought and won the tournament.

At Bellator 85, Pitbull came up short in his title shot as defending champion Pat Curran won via split decision. 

After putting together another win streak of 4 fights, Pitbull once again challenged champion Pat Curran to a rematch at Bellator 123. This time the result came out differently as Friere walked away with the decision and the Bellator Featherweight Championship. 

Friere's next fight would also be his first title defense as he faced Daniel Straus at Bellator 132. In a competitive fight it was Friere who would walk away victorious as he submitted Straus with a rear naked choke in the fourth round to defend his Featherweight championship.

Friere's second title defense was against Daniel Weichel at Bellator 138 on June 19, 2015. His original opponent was set to be Georgi Karakhanyan in a rematch of their Bellator 37 contest, but Karakhanyan suffered a torn ACL and Weichel was brought in as his replacement. In the opening round Weichel came out aggressively and succeeded in dropping the champion at the end of the first round. The first thirty seconds of the second round mirrored the end of the first, with Weichel coming out looking for the finish with strikes. At the thirty-second mark of the second round Friere landed with a devastating counter left hook that dropped Weichel and ended the fight via KO. The win marked Friere's second successful defense of his Featherweight crown.