For climate and sustainability reasons, there is an interest and incentive to produce plastic and rubber products with increased content of a bio-based component, preferably existing as an industrial by-product, for example, wood powder/sawdust. There are many studies on the making of wood-plastic composites, but hitherto very few consider vacuum forming as a processing technique, especially considering a biofiller. Here, the properties of a vacuum formed composite with thermally modified wood powder (with reduced water uptake) and a very ductile polyolefin, was reported. Surprisingly, even at a 15 wt% filler content, the composite remained ductile (extensibility of ca. 30%). The water uptake increased with increasing content of wood powder, but was never more than 5%. The water sorption kinetics indicated that the wood powder did not form a percolated continuous path through the material for easy access to the water, which led to a low water diffusivity (ca. 2 × 10−10 cm2 s−1). The calorimetric data showed that the biofiller, overall, did not affect the melting and crystallization behavior of the polymer matrix, nor the observed glass transition temperature. To conclude, vacuum forming was shown to be a viable technique for composites with a very ductile/elastic matrix and stiff fillers.