The invention relates to a method for preparing natural fibre-based composite materials containing natural binders and powdery proteins, comprising the following steps; adding a powdery protein adhesive binder to natural fibres having a moisture content of 1 15%; mixing the natural fibres together with the powdery protein adhesive; adjusting the moisture content of the composition to 6 24% w/w; and submitting the mixture to a heat pressure treatment to form the natural fibre-based material.