Composite materials were prepared from recycled PP and woodflour. The effects of various factors (e.g., the particle size of the woodflour and the concentrations of woodflour, coupling agent-i.e., a mixture of maleic anhydride and dicumyl peroxide-and impact modifier) as well as fire-retardant materials [e.g., mixture of boric acid, Na-borate, and Mg(OH)₂] on the mechanical properties of the composites were evaluated. In general, the mechanical properties of the surface-modified woodflour-filled composites were superior to those of unmodified ones. The effects of each component and interactions between them were also statistically analyzed based on an empirical model. The significance of the model coefficients was discussed. In most cases, good correlation of the results was obtained.