Part of the loft space of a detached, three-storey pub is alight.
Station Commander Chris Brown, who is at the scene, said: “Firefighters are tackling the fire internally and are being assisted by an aerial appliance.
“Nine people left the building before the Brigade arrived and are thankfully, all uninjured.
“Crews are continuing to work to bring the fire under control and are carrying out salvage operations.
“Orpington High Street is closed whilst crews work to make the scene safe and we urge people to avoid the area.”
The Brigade was called at 7.30am on Tuesday morning, Fire crews from Sidcup, Orpington, Bromley and surrounding fire stations are at the scene.
The cause of the fire is not known at this time.