Firefighters were called to Ashfield Stadium in Possilpark, the home of Glasgow Tigers speedway club, yesterday morning.
The club has warned the extent of the damage throws into question whether they will be able to reopen next season.
Police Scotland has confirmed that they believe the fire was started deliberately.
Thousands of pounds were invested in the stadium bar after new owners took over at the end of last season.
Two temporary bar units, installed in March, have been severely damaged and furniture, televisions and bar stock has all been destroyed.
A farewell meeting for club legend James Grieves - who has retired after a 23-year career in the sport -planned for Sunday, October 20, may now have to be cancelled.
Craig McCurdy, Glasgow Tigers' co- director, said the fire was a "painful blow" to the club.
He said: "Hopefully the club can come back from this."
A Police Scotland spokeswoman said there was also a break-in at the stadium.