Twelve fire engines and around 80 firefighters have been in attendance at a fire next to the North Circular Road in Neasden.
A ground floor workshop was destroyed by fire with the fire spreading to offices above and the building's roof. There have been no reports of any injuries.
Station Commander Gary Melia, who was at the scene, said: "Crews worked through the night in hot and arduous conditions to bring this fire under control. Firefighters remained on scene the following day to dampen down and fully extinguish the fire.
"We deployed two of our 32-metre turntable ladders as water towers to help extinguish the fire from height.
"We advised people working and living in the area to keep their windows and doors closed due to smoke being produced from the fire.
"The A406 North Circular remained open in both directions; however lane closures westbound did cause some significant traffic disruption, between the junctions of Staples Corner and the A4088, as well as on Waterloo Road whilst the incident was ongoing."
The Brigade received the first of 25 calls about the fire at 2320 and Control Officers mobilised crews from Willesden, Hendon, Finchley, Mill Hill, Wembley, Park Royal, West Hampstead, Stanmore and surrounding fire stations to the scene.
Two 32-metre turntable ladders from Wembley and Paddington fire stations were also in attendance during the early stages of the incident.
The fire was brought under control by 0205.
The cause of the fire has been recorded as undetermined.