This article deals with the effects of surface-modified talc particles on mechanical properties of polypropylene (PP)/talc composites. These materials were prepared by injection molding of PP blended with different concentrations of nontreated and treated talc, under the same processing conditions. Differential thermal calorimetry and scanning electron microscopy were used to assess thermal properties and morphology of the final composites. The reinforcing effect of talc, either treated or nontreated surface, on PP is analyzed through the tensile properties as a function of the mineral content (010 wt%). Morphological structure of composites revealed that the talc treatment improved the particle dispersion and distribution within the PP matrix and enhanced the interfacial PP-talc adhesion. The mechanical properties of these composites, especially the Young modulus, tensile strength and elongation at break, were found to be improved respect to PP-untreated talc ones. POLYM. ENG. SCI., 2013. (c) 2012 Society of Plastics Engineers