Sources close to the situation told ESPN the bout is not yet official, but verbal agreements are in place. MMAJunkie.com first reported the fight was set.
The heavyweight clash is expected to headline the UFC 220 pay-per-view event, which also will feature a previously announced light heavyweight title bout between Daniel Cormier (19-1) and Volkan Oezdemir (15-1). The event will take place inside TD Garden.
Miocic (17-2) will attempt to become the longest-reigning heavyweight champion in UFC history. He tied the division's all-time record of two consecutive title defenses in May with a knockout win over Junior dos Santos.
Fighting out of Cleveland, Miocic asked the UFC to restructure his contract earlier this year. The defending champ has not yet stated whether that happened.
Ngannou (11-1) is coming off a first-round knockout win over Alistair Overeem at UFC 218 last weekend. It's a very quick turnaround for Ngannou, but one he agreed to even before his recent highlight-reel finish in Detroit.
The Cameroonian-French heavyweight trains out of the UFC Performance Institute in Las Vegas. Both he and Miocic have finished their past four opponents in the first round.