Five fire engines and around 30 firefighters tackled a fire at an office block on Lower Thames Street in Dowgate.
Part of a plant room on the ninth floor was damaged by the fire. Four people left the building before the arrival of the Brigade. There were no reports of any injuries.
The cause of the fire is believed to be electrical.
The Brigade was called at 0646 and the incident was over by 0856. Firefighters from Dowgate, Whitechapel, Dockhead and Shoreditch Fire Stations attended the scene.