Five fire engines were called to a commercial building on Shambles Street in Barnsley at 3pm on Thursday afternoon.
The fire was on the first floor of the building which is believed to be used as an accountants office.
Crews from Barnsley, Cudworth, Dearne and Tankersley fire stations arrived to find the fire well alight and the roof also involved.
Firefighters worked quickly to bring the fire under control.
Fire crews left the scene at 5:30pm.
An investigation into the cause of the fire is ongoing, however first indications are that this was an accidental fire.