This study investigated the surface roughness and wettability of polypropylene composites filled with Paulownia elongata wood flour with and without maleic anhydride-grafted polypropylene at different wood flour contents (30, 40, 50, and 60 wt%). The surface roughness values of the filled polypropylene composites decreased with increasing content of the polypropylene. The polypropylene composites without the maleic anhydride-grafted polypropylene were found to have higher surface roughness but better wettability as compared with the ones with the maleic anhydride-grafted polypropylene. The wettability of polypropylene composites increased with increasing content of the wood flour. The incorporation of the coupling agent in the polypropylene composites decreased the wettability of the specimens compared with untreated ones. The test result showed that P. elongata wood flour could be utilized in the production of the filled polypropylene composites because of their satisfying surface properties of the composites.