Five fire engines are tackling a blaze close to a garden centre on Doncaster Road, Thrybergh.
Crews were called to the incident shortly before 9pm on Tuesday (22 May).
A building around 40 metres by 20 metres in size is well alight.
Around 25 firefighters are using hose reels to tackle the blaze.
Residents are being advised to keep windows and doors closed.
An investigation into the cause of the incident will begin once the fire has been extinguished.