The blaze broke out shortly after 6pm on Monday at the Nanoscience and Technology Building on Broad Lane in Sheffield city centre.
The incident is believed to have started in a third-floor laboratory at the North Campus department.
Fire crews used breathing apparatus and hoses to control the fire.
The university said it was aware of the fire and emergency services were dealing with the situation, adding: “We advise our staff, students and members of the public to stay away from the area.”