Four fire engines and around 25 firefighters tackled a flat fire on Blenheim Gardens in Willesden Green.
Half of a three-roomed flat on the third floor of a four-storey block was damaged by fire. Three people were led to safety from the third floor by fire crews wearing breathing apparatus. There were no reports of any injuries.
The Brigade was called at 1840 and the fire was under control at 1920. Fire crews from Willesden, West Hampstead and North Kensington fire stations were in attendance.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.