At 5am six fire engines and 35 fire fighters arrived at the The Archway Sheet Metal Works, near White Hart Lane.
Owners of the 25,000 sq ft site have been in talks with the football club who have been trying to buy the building for more than 10 years.
Spurs football club were hoping to finish the new 56,000 seat stadium by 2017-2018, despite not making a deal with the metal works building.
London Fire Brigade said half of the ground floor and the whole of the first floor were alight.
The blaze was brought under control at about 8am.
Some media outlets are reporting that arsonists could have been behind the fire.
London Live’s Jake Tupman, was at the scene.