Fifteen fire engines and around 100 firefighters tackled a flat fire on Inglewood Road in West Hampstead.
Most of a five-roomed flat on the fourth floor and most of a four-roomed flat on the fifth floor were damaged by the fire.
Station Manager Claiton Murray said:
"The fire is believed to have started in a flat on the fourth floor. The flat was severely damaged by fire and a large part of the roof was also destroyed. In the early stages the fire was very visible and could be seen for miles around.
"Due to concerns that the roof could collapse inward firefighters evacuated residents from the top floor. In addition fire crews assisted two people from the first floor and a number of other residents self evacuated from lower floors. Around 50 residents used a local public house as a rest centre.
"The London Ambulance Service have confirmed that no one was taken to hospital as a result of this incident. Firefighters have carried out salvage operations to save where possible residents possessions from water damage."
The Brigade was called at 0104 and the fire was under control by 0501. Fire crews from West Hampstead and surrounding stations were at the scene.
The cause of the fire is under investigation.