Twelve fire engines and around 80 firefighters have been in attendance at a fire next to the North Circular Road in Neasden.
The roof and most of the first and ground floors of the warehouse have been destroyed by fire. There have been no reports of any injuries.
Station Commander Gary Melia, who is at the scene, said: "Crews have been working through the night in hot and arduous conditions to bring this fire under control. Firefighters remain on scene this morning dampening down to 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 is open in both directions, but some traffic disruption can be expected westbound, between the junctions of Staples Corner and the A4088, as well as on Waterloo Road whilst the incident is ongoing and as we head towards rush hour."
The Brigade received the first of 25 calls about the fire at 2320 and Control Officers have 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 are also in attendance.
The fire was brought under control by 0205.
The cause of the fire is under investigation.