Half of the ground floor of the five-story building in Craven Road, Paddington, is on fire, according to the London Fire Brigade at 5.30 p.m. on Thursday.
The brigade was called to the scene at around 4.40pm.
There are ten fire engines on the scene, including crews from Paddington, Kensington, North Kensington, Euston, and other nearby stations.
Road closures are in place, and people are asked to avoid the area as much as possible,” an LFB spokesperson said.
“At this time, the cause of the fire is unknown.”