Four fire engines and 21 firefighters and officers were called to a fire at a flat in Jamaica Street, Shadwell.
Half of a fourth-floor flat was damaged by fire. A woman left the premises before the Brigade arrived. Firefighters rescued a cat from the property and administered oxygen before handing the animal over to the RSPCA.
The Brigade was called at 0248 and the fire was under control at 0356. Fire crews from Shadwell, Bethnal Green, Poplar, and Millwall fire stations attended the scene.
The cause of the fire is under investigation.