Four fire engines and around 25 firefighters tackled a flat fire on Laleham Avenue in Mill Hill.
Part of the ground floor of a semi-detached house converted into flats was damaged by fire. One man left the building before the Brigade arrived and was treated on scene after suffering from smoke inhalation.
The Brigade was called at 1447 and the fire was under control by 1540. Fire crews from Mill Hill, Hendon, Stanmore and Tottenham fire stations attended the scene.
The cause of the fire is under investigation.