Polypropylene (PP) and waste tire dust (WTD) were internally mixed with various amounts of short glass fiber (SGF) to form a series of PP/WTD/SGF composites, with and without addition of a silane coupling agent, γ-aminopropyltrimethoxysilane (γ-APS), and dynamic vulcanization (DV). The effects of γ-APS, and DV on the properties of the composites were investigated. The PP/WTD/SGF composites were prepared by using WTD of 250–500 μm dimensions at different SGF loadings (5, 10, 15, and 20 parts per hundred parts of polymer). The results revealed that the addition of γ-APS and DV increased the equilibrium torque, tensile properties except elongation at break, and swelling resistance of the composites. Because of the incorporation of γ-APS and DV, the thermal stability was enhanced, and scanning electron micrographs showed improved adhesion between the PP/WTD matrix and SGF. Analysis by Fourier transform infrared was performed on the composites with and without addition of γ-APS and DV in order to study the interactions among the PP, WTD, SGF, and the amino functional group of the silane. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers.