Assuncao announced the news via Twitter on Tuesday.
"I just got cut from the UFC," he wrote. "Apparently they did not like my last fight. I'm not in control of all this. Thanks UFC for the opportunity.
"The boss himself told me the fight was good, got a performance (bonus), was in a good win streak before that last fight. I don't understand."
The 30-year-old went on to attribute the decision towards "politics behind scenes" and say he had "no leverage to argue with the UFC."
"Maybe it was personal," Assuncao explained. "There wasn't any improper behavior. I'm not the one talking to the UFC so I'm helpless on this decision."
Assuncao is now 2-3 over two stints inside the UFC, with notable losses to Pearson, Nate Diaz, and Kurt Pellegrino. The Pearson fight, in particular, was as hard-fought of a loss as they come, and marked the first time the Brazilian tasted defeat since mid-2008.