Four fire engines and around 25 firefighters tackled a fire at a hostel on Priory Park Road in Queens Park.
A room on the second floor was badly damaged. A man was suffering from smoke inhalation and taken to hospital by London Ambulance Service crews.
The Brigade was called at 0520 and the fire was under control by 0639. Fire crews from West Hampstead and North Kensington fire stations were at the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.