Ten fire engines and around 70 firefighters were called to a hotel fire on Tooley Street near Tower Bridge.
Part of a room on the 10th floor of the building was alight. There are currently no reports of any injuries.
Station Commander Paul Morgan, who was at the scene, said: “Crews worked quickly to contain the fire and stop it from spreading further.
“Crews are expected to remain on scene throughout the evening.
“Road closures are in place whilst firefighters continue to make the scene safe and we ask people to avoid the area.”
The Brigade was called at 1734 and the fire was under control by 1829. Fire crews from Dockhead, Old Kent Road, Lambeth, Bethnal Green, Dowgate and surrounding fire stations attended the scene.
The cause of the fire is under investigation