Effect of different compatibilizers and magnesium hydroxide (MH) on morphology, thermal stability and mechanical properties of polypropylene (PP) composites were investigated in this study. Two different types of compatibilizers namely, polypropylene grafted-maleic anhydride (PP-g-MA) and ethylene-octene copolymer grafted-maleic anhydride (POE-g-MA) were used in this study. The results indicated that the degradation of PP/MH composites contained two steps: decomposition of MH and degradation of macromolecular. MH particles acting as physical barrier improved the thermal stability of PP, especially in oxygen. POE-g-MA enhanced it furthermore. Introduction of PP-g-MA or POE-g-MA to PP/MH composites resulted in considerable improvement in mechanical properties. The addition of PP-g-MA was most effective in increasing the tensile strength, while addition of POE-g-MA greatly increased the impact strength of PP/MH composites. Morphological investigation revealed that the improvement was attributed to the formation of encapsulation structure in these compatibilized PP/MH composites. (C) 2008 Elsevier B.V. All rights reserved.