Ten fire engines and around 70 firefighters were called to a fire at a disused golf club on Brockley Hill in Edgware.
A derelict two-storey clubhouse and part of the driving range were alight. There were no reports of any injuries.
Station Commander Neil Guyett, who was at the scene, said: “On arrival crews were faced with a well developed fire, rapidly spreading through the building.
“Firefighters worked hard to bring the fire under control.
“There was a large amount of smoke in the area so local residents and businesses were advised to keep their doors and windows closed.
“The fire is now under control, but crews will be on scene throughout the morning and local road closures remain in place.”
The Brigade was called at 12.29am and the fire was under control by 2.40am. Fire crews from Stanmore, Mill Hill, Hendon, Harrow, Barnet and surrounding fire stations were at the scene, along with colleagues from Hertfordshire Fire and Rescue Service.
The cause of the fire is under investigation.