In this study, polypropylene grafted with maleic anhydride (PP-g-MA) and styrene ethylene-co-butylene styrene block copolymer grafted with maleic anhydride (SEBS-g-MA) were used as coupling agents for polypropylene-based woodplastic composites containing 50 wt % wood flour. Adding up to 5 wt % PP-g-MA to the composite increased the tensile strength of the wood-plastic composite (WPC) by almost 100% and the reversed-notch Izod impact strength by more than 100%; the modulus remained essentially unchanged. By contrast, the same amount of SEBS-g-MA had a greater effect on the impact strength but a smaller influence on the tensile strength; in addition, the modulus was reduced. On using a combination of 2 wt % PP-g-MA and 1 wt % SEBS-g-MA, the impact strength of the composite could be increased significantly, but the tensile strength and modulus were not reduced to any appreciable extent relative to the use of PP-g-MA alone. Because WPCs are building products where minimizing costs is extremely important, this finding has important commercial implications. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013