London Fire Brigade (LFB) said 10 engines and 70 firefighters were called to the site in Dorris Hill Lane, Neasden, at around 4am
Half of the first floor, second floor and roof of the hall were said to be alight.
The fire was under control around 7:15 am.
Crews were sent from Willesden, West Hampstead, Wembley, North Kensington, Hendon and surrounding stations, LFB said.
The cause of the fire remains unclear.
The Metropolitan Police said in a tweet: "We are on scene at Neasden Circle junction with Tanfield Avenue for a fire at a Church. Tanfield Avenue and part of Neasden Circle remain closed."
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