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 destroyed by the fire. 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 Brigade was called at 0029 and the fire was under control by 0240. 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 has been recorded as undetermined.