Four fire engines and around 25 firefighters were called to a maisonette fire on Bournebrook Grove in Romford.
Part of a split-level maisonette on the third and fourth floors of the building was damaged by fire. One man left the building before the Brigade arrived and was treated on scene by London Ambulance Service crews after suffering from smoke inhalation.
The Brigade was called at 1120 and the fire was under control by 1156. Fire crews from Dagenham, Romford, Hainault and Harold Hill fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.