Eight people were led to safety by firefighters following a blaze at a hostel in Pinner Road in Harrow.
A kitchen on the first floor of the property was destroyed by fire. A resident raised the alarm after smelling smoke.
Watch Manager Dave Kelly, who attended the scene, said: "When crews arrived they were faced with a fire in the kitchen. Ten people had left the property before we arrived and crews led eight other residents to safety and quickly extinguished the fire."
The Brigade was called at 01:17 and the fire was under control at 02:15. Four fire engines and around 25 firefighters from Harrow, Northolt and Wembley Fire Stations attended the incidents.
The cause of the fire is under investigation.