Calgary fire crews were at a blaze in an unoccupied and boarded-up building on Fourth Avenue S.W. in downtown.
Firefighters were met with flames and smoke billowing from the third floor just after 8 p.m. Thursday evening.
They attacked the fire from inside and put it out, containing the damage to one area, a battalion chief confirmed.
No one was injured.
Several streets in the area have been blocked off.
The cause of the fire remains under investigation.