Six fire engines and around 40 firefighters tackled a fire at a maisonette on Highbury Quadrant in Islington.
Most of the third floor of a split-level maisonette was damaged by fire. A man and a woman left the building before the Brigade arrived and were assessed on scene by London Ambulance Service crews.
Station Commander Emma Carr, who was at the scene, said: "Firefighters worked quickly to bring the fire under control. Crews used one of the Brigade's 32-metre turntable ladders to check for any remaining hot spots in the roof of the property.
"The affected maisonette was heavily smoke logged.
"There were road closures in place whilst crews made the scene safe. Thankfully, there were no reports of any injuries."
The Brigade was called at 1421 and the fire was under control by 1531. Fire crews from Shoreditch, Tottenham, Holloway, Stoke Newington and Hornsey fire stations attended the scene.
The cause of the fire is under investigation.