Six fire engines and around 40 firefighters were called to a flat fire above a shop on Cranbrook Road, Ilford.
Half of the first floor and roof were damaged, firefighters used an aerial ladder platform and a drone to tackle the blaze.
The Brigade was called at 1544 and the fire was under control at 1902. Fire crews from Hainault, Ilford, Woodford, Stratford and Dagenham attended the scene.
The cause of the fire is believed to be packaging materials left too close to a hob cooker, which was switched on.