Over the past few years, the interest towards environmental sustainability by both academic and industrial research has grown more and more. A class of materials that meets the demand for a lower environmental impact are Wood Polymer Composites, or WPC. These materials are composed of a thermoplastic polymer mixed with wood flour, usually coming from processing waste. With these materials, the greatest benefit is obtained by increasing the wood content and reducing the percentage of polymeric matrix. On the other hand, two of the main drawbacks coming from an increase in the wood content are brittleness and a significant reduction in processability: this is due to viscosity increase, higher porosity in the final product and higher risks of thermo-oxidative degradation. In this work we will concentrate on brittleness. As this can often be reduced by blending with elastomers, we will evaluate the effects of different percentages of a thermoplastic elastomer (Santoprene by EXXON Mobil) blended into a polypropylene based WPC filled with 50 wt.% of wood. For each material, different extrusion conditions have been studied, such as a starve vs. flood fed feeding condition and varying the speed of the screw. Next, the optimal combination of processing conditions and elastomer content was obtained by measuring the mechanical properties in tension and the density of all materials. Our results indicate that the best compromise in terms of strength, stiffness and ductility were obtained by using 10 wt.% of Santoprene. From the processing conditions point of view, if flood feeding is chosen, the blend needs to be processed at a reduced screw speed in order to avoid air bubbles and surface defects, while in starved conditions, properties seem to be better independently of screw speed.