In this study, various polypropylene (PP) nanocomposites were prepared by melt blending method. The effects of different spherical nanofillers, such as 50 nm CaCO(3) and 20 nm SiO(2), on the linear viscoelastic property, crystallization behavior, morphology and mechanical property of the resulting PP nanocomposites were examined. Rheological study indicated that wcoincorporation of nano-SiO(2) and nano-CaCO(3) favored the uniform dispersion of nanoparticles in the PP matrix. Differential scanning calorimeter (DSC) and polarizing optical microscopy (POM) studies revealed that the coincorporation of SiO(2) and CaCO(3) nanoparticles could effectively improve PP crystallizability, which gave rise to a lower supercooling temperature (Delta T), a shorter crystallization half-life (t(1/2)) and a smaller spherulite size in comparison with those nanocomposites incorporating only one type of CaCO(3) or SiO(2) nanoparticles. The mechanical analysis results also showed that addition of two types of nanoparticles into PP matrix gave rise to enhanced performance than the nanocomposites containing CaCO(3) or SiO(2) individually. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121:3007-3013, 2011