The physicomechanical properties, thermal properties, odor, and volatile organic compound (VOC) emissions of natural-flour-filled polypropylene (PP) composites were investigated as a function of the zeolite type and content. The surface area and pore structure of the natural and synthetic zeolites were determined by surface area analysis and scanning electron microscopy, respectively. With increasing natural and synthetic zeolite content, the tensile and flexural strengths of the hybrid composites were not significantly changed, whereas the water absorption was slightly increased. The thermal stability and degradation temperature of the hybrid composites were slightly increased with increasing natural and synthetic zeolite content. At natural and synthetic zeolite contents of 3%, the various odors and VOC emissions of the polypropylene/rice husk flour and polypropylene/wood flour hybrid composites were significantly reduced because of the absorption of the odor and VOC materials in the pore structures of the natural and synthetic zeolites. These results suggest that the addition of natural and synthetic zeolites to natural-flour-filled thermoplastic polymer composites is an effective method of reducing their odor and VOC emissions without any degradation of their mechanical and thermal properties. (C)2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3247-3255, 2008