Four fire engines and around 25 firefighters responded to reports of a fire at a derelict pub on Church Road in Leyton.
A single storey self contained annex at the rear of the building was destroyed by the fire. One woman was treated on scene by London Ambulance Service crews.
The cause of the fire is under investigation.
The Brigade was called at 1708 and the incident was over for firefighters at 1809. Firefighters from Leyton, Leytonstone, Walthamstow and Stoke Newington fire stations attended the scene.