Six fire engines and around 40 firefighters attended a fire at a five-storey residential block on Harrow Road in Wembley.
Half of a flat on the fourth floor was destroyed by fire, with a neighbouring flat sustaining some partial damage. An adjoining balcony was destroyed by fire.
The building was safely evacuated by firefighters and there were no reports of any injuries.
The Brigade received the first of eight calls at 2157 and Control Officers mobilised crews from Wembley, Northolt, Harrow and Stanmore fire stations to the scene. A 32-metre turntable ladder from Wembley Fire Station also attended and was deployed as an observation tower, providing the Incident Commander with a greater situational awareness of the incident.
The fire was brought under control by 2240.
The cause of the fire has been recorded as undetermined.