The fire happened just before midnight at Bertucci's Restaurant in the 900 block of Baltimore Pike.
A cleaning crew working inside saw smoke and dialed 911.
Arriving firefighters discovered a fire in the exhaust vent located in the wall between Bertucci's and neighboring 5 Below store.
Firefighters were forced to open up the walls to get to the fire and were able to quickly bring it under control.
No injuries were reported.