Prior to his star-making career inside the Zuffa, LLC-owned WEC promotion, Mike Thomas Brown made his name on the local MMA circuits of New England, Ohio, and Florida, running his professional record to an impressive 18-4 with notable victories over Mark Hominick and Yves Edwards. After defeating favorite Jeff Curran in his WEC debut in 2008, Brown was matched up with the man many considered one of the best fighters in the world pound-for-pound, WEC Featherweight Champion Urijah Faber. Brown knocked Faber out in the first round to take the featherweight championship in a major upset. He then defeated Leonard Garcia in the first round of his first title defense, and defeated Faber for a second time in their 2009 rematch over five rounds. Brown is known for his physical strength, suffocating top game, and knockout power. Brown would lose the WEC belt in his next fight against Jose Aldo. He fought 3 more times in the WEC before the merger sandwiching a submission & a KO win around his KO loss to Gamburyan..

Brown dropped his first two fights upon his return to the UFC to Diego Nunes and Rani Yahya before righting himself and earning decision victories over Nam Phan and Daniel Pineda. He fought sporadically after the Phan fight as he focused on coaching full-time at American Top Team rather than making his fighting career his primary goal. He lost in less than a minute in his last bout against Steven Siler, bringing his overall UFC record to 2-4.

Brown was scheduled to face Estevan Payan at UFC on FOX 11 before he was removed from the card due to injury. He has since stated that he believes he is likely done with fighting at this juncture.