At the scene crews were able to stop the fire spreading to a nearby building, but the spokesman said "there's nothing left" of the chicken shed.
Seven fire appliances from Whanganui, Palmerston North, Ratana, Marton and Waverley attended the scene alongside three water tankers and a rural Fire and Emergency unit.
Water from a nearby swimming pool was also used to put out the blaze, and crews at the scene were damping down hotspots by 2.30am.
A specialist Fire and Emergency investigator was working to determine the cause of the fire.