Four fire engines and around 25 firefighters tackled a fire at a restaurant with flats above on Baker Street in Marylebone.
Part of a ground floor restaurant was damaged by the fire. Firefighters wearing breathing apparatus rescued eight people from the building using fire escape hoods. Four people were taken to hospital by London Ambulance Service crews.
Fire escape hoods provide members of the public with up to 15 minutes protection from four of the main fire gases (carbon monoxide, hydrogen cyanide, hydrogen chloride and acrolein) and can be worn by conscious or unconscious people.
The Brigade was called at 0004 and the incident was over for firefighters at 0209.
Firefighters from Euston, Paddington and Soho fire stations attended the scene.
The fire is believed to have been accidental and caused by an electrical fault.