The purpose of this study was to improve the mechanical properties (such as tensile, flexural, and impact strength) of rice hull/polypropylene composites, with the use of styrene-ethylene-butylene-styrene copolymer (SEBS) and maleated styrene-ethylene-butylenestyrene copolymer (SEBS-MA). The results suggested that both types of additives increased the impact strength of the composites significantly as their contents increased. However, only SEBS-MA improved the tensile and flexural strength of the composites. The results also indicated that the composites with SEBS-MA consistently showed better mechanical properties than the SEBS counterparts for all the contents.