The George IV pub in Hunslet closed in July when its licence was suspended amid concerns that it was being used as a weapons and drugs den.
After hearing evidence from police on July 18, a Leeds City Council panel ordered a three month suspension which would have expired today.
However, firefighters were called to the pub in Grove Road at around midnight following reports of a blaze.
Crews from Leeds and Hunslet found the first floor and roof were alight.
Firefighters wearing breathing apparatus entered the building and used two large jets to put out the flames.
A West Yorkshire Fire service spokeswoman said the cause of the fire was now under investigation.