Part of a four-roomed flat on the fourth floor of the building was damaged by fire.
The London Fire Brigade said it was called at just before 5pm on Saturday.
Fire crews from West Hampstead, North Kensington, Willesden, Paddington, Kentish Town and surrounding fire stations are at the scene.
Station Commander Jonathon Holt, who was at the scene, said: “Firefighters worked quickly to bring the fire under control.
“One woman was taken to hospital by London Ambulance Service crews.
“There were road closures in place whilst firefighters worked to make the scene safe and buses were on diversion.”
The cause of the fire is under investigation.
Roads which surround Abbey State Tower have been closed after a fire was reported.
The B507 Abbey Road (NW6/NW8) in both directions is closed from the junction of Belsize Road.