Twelve fire engines and around 80 firefighters have been called to a fire at a leisure centre in Highbury Crescent in Highbury.
Part of the roof of the single-storey building is alight.
The Brigade was called at 1203. Fire crews from Islington, Holloway, Stoke Newington, Paddington and surrounding fire stations are at the scene.
The cause of the fire is not known at this stage.