Twelve fire engines and around 80 firefighters were called to a fire at a leisure centre in Highbury Crescent in Highbury.
Most of the roof of the single-storey building was damaged by the fire. Around 100 members of the public and staff left the building before the Brigade arrived. There were no reports of any injuries.
Station Manager James Chapman, who was at the scene, said: “Crews worked hard in difficult conditions to bring this large fire under control.
“A number of local road closures were in place around the site and motorists were advised to avoid the area if possible.”
The Brigade was called at 1203 and the fire was under control by 1447.
Fire crews from Islington, Holloway, Stoke Newington, Paddington and surrounding fire stations attended the incident.
The cause of the fire is believed to be from hot works being carried out on the roof.