Three fire engines and around 15 firefighters were called to a fire at a shop with flats above on Watford Way in Mill Hill.
Part of a bedsit on the second floor was damaged by fire. Firefighters wearing breathing apparatus rescued one man via an internal staircase. He was treated on scene after suffering from smoke inhalation.
The Brigade was called at 2344 and the fire was under control by 0018. Fire crews from Mill Hill and Hendon fire stations attended the scene.
The cause of the fire is under investigation.