The effects of mineral fillers on the fire retardancy of wood-polypropylene composites have been studied. Wood-polypropylene composites containing mineral fillers have been compounded in a conical twin-screw extruder. A composite manufactured without any mineral filler addition has been used as a reference. The flame resistance properties of the composite materials have been studied using the cone calorimeter. The results show that the introduction of mineral fillers into the wood-polypropylene composites has a favourable effect on the fire resistance properties of the composite materials. The reaction-to-fire properties have been improved according to the fire classification of construction products based on the Euroclass system. Copyright © 2012 John Wiley & Sons, Ltd.