Firmino began his career at the tenth edition of the World Vale Tudo Championship in Recife, Brazil when he was 18 years old. The tournament was held in one night and was fought under Vale Tudo-style rules. After defeating Reginaldo Santana and Sergei Bytchkov, he reached the final and faced Eli Soares. The fight lasted for thirty minutes with no breaks and Soares won by decision. Firmino then returned two years later at the M-1 Global event MFC: Russia vs the World 3 in Saint Petersburg, Russia where he again beat Sergei Bytchkov, by technical knockout in the second round. At Russia vs the World 5 the following year, he defeated Musail Allaudinov via unanimous decision after one fifteen-minute round. After winning his next four bouts - three by submission - he was given a chance to compete in the Pride Fighting Championships.
Pride Fighting Championships
Firmino faced off against Hiroyuki Abe at his first Pride fight, Pride Bushido 4 in July 2004, and won by using an arm triangle choke in the first round. Firmino then returned against Masakazu Imanari three months later at Pride Bushido 5 at won by unanimous decision. After this early success, he lost his next two bouts by decision in 2005. In November 2006, Firmono took on Nobuhiro Obiya at Pride Bushido 13 and won the fight by yet another unanimous decision.
Dream
Pride FC then shut down, however, and Firmino soon signed with Dream. He made his debut with the organization at its first event, Dream 1, in March 2008 where he submitted Kazuyuki Miyata with a rear-naked choke seven minutes into the first round. At Dream 3two months later, he was given the opportunity to avenge his earlier loss to Tatsuya Kawajiri. He was unable to do this, however, and was beaten on a unanimous decision.
Post-Japan
Firmino then left Dream after this, and won his first fight outside Japan in five years when he beat Ryan Healy in Miami, Florida at Shine Fights 2: ATT vs. The World in September 2009. Firmino also returned to fight in his native Brazil for the first time in almost seven years when he faced Francisco Trinaldo at Bitetti Combat MMA 6, where he was submitted with a kneebar. Firmino competed at Superior Cage Combat 3, where he lost against UFC and Pride veteran, Canadian John Alessio via decision. Firmino defeated alumni Johnavan Vistante by submission due to an arm-triangle choke in the first round at CFA 07: Never Give Up in Coral Gables, Florida on June 30, 2012. Firmino defeated two-time Bellator Tournament finalist, and 2009 Submission of the year winner Toby Imada by unanimous decision at CFA 08 in Hollywood, Florida on October 6, 2012. Firmino faced Bellator veteran Luis Palomino on January 19, 2013 for the CFA Lightweight Championship, Firmino dominated Palomino with his Wrestling and ground and pound to take home the CFA Lightweight Championship by unanimous decision. Firmino vacated the title in September 2013 when he signed with World Series of Fighting.
Firmino made his WSOF debut against Jacob Volkmann at WSOF 6 on October 26, 2013. He won the fight via unanimous decision. He then faced UFC veteran Tyson Griffin at on June 21, 2014. He won the back-and-forth fight via unanimous decision. After almost two years away from the promotion, Firmino returned in January 2016 to face Strikeforce and UFC veteran Caros Fodor at. He won the fight by unanimous decision. Firmino faced Brian Foster at WSOF 33 on October 7 in Kansas City, Missouri. He lost the fight by submission in the first round. Firmino stepped in for an injured João Zeferino to take on WSOF Lightweight ChampionJustin Gaethje at. After a back-and-forth three rounds, the bout was stopped by the doctor between rounds three and four due to Firmino's swollen right eye; the end result was a TKO loss for Firmino.
The Ultimate Fighter
Firmino was as a cast member for representing Blackzilians He defeated Uros Jurisic by unanimous decision to win 25 points for his team.
