The multi-alarm fire broke out just before 4 p.m. at the Oak Park Mart Shell gas station in the 6800 block of Glenwood Avenue, near Duraleigh Road.
Heavy smoke and flames poured from the roof of the building until firefighters were able to get enough water on it from ladder trucks to control the flames.
Fire officials believe the blaze started in a shed behind the convenience store and spread to the attic of the structure.
Store employees and fire crews were able to keep the flames from moving to the gas pumps and a propane display in front of the store.
At one point, traffic on Glenwood Avenue had to be stopped so fire crews could use hydrants on the other side of the road.
The fire was brought under control just before 5:30 p.m.
Damage to the building was extensive.
No one was injured.