At the height of the fire, nine appliances and about 30 firefighters battled to contain it.
Fire and Emergency New Zealand shift manager Jill Higgison said the first crew, from Waitahuna, had arrived to finda shed "well alight" off Mount Stuart Rd.
It was decided to immediately escalate the response to "third alarm" and further crews arrived from Milton, Lawrence, Clutha and Balclutha, Higgison said.
Three buildings on the farm caught fire, but firefighters were able to quickly extinguish two and contain the blaze to one 40m x 10m shed.
The Otago Daily Times had been unable to confirm the name of the property, but the fire occurred between Roberts Rd and Burma Rd intersections on Mount Stuart Rd, Johnston.
Pioneer Energy, owner a wind farm on the opposite side of the road, confirmed the fire had not affected its infrastructure.