The oxygen permeation properties of polypropylene nanocomposites were examined to compare their oxygen-barrier performance as affected by temperature (25-50 degrees C), relative humidity (0-50% RH), and nanoparticle contents. Polypropylene/ clay, polypropylene/ ZnO composites and polypropylene/clay/ZnO ternary nanocomposites were prepared with different compositions by melt compounding to determine the optimum amount of nanoparticles. The results showed that at low temperatures, the effect of both clay and ZnO nanoparticles on oxygen barrier properties of polypropylene was very low. The resulting PP nanocomposites showed increase in oxygen permeability as temperature increased, with an Arrhenius behavior, and activation energy of 43.9-44.7 kJ/mol. The differential scanning calorimetry results indicated that the addition of clay and ZnO nanoparticles in composites slightly decreased melting temperature (T-m) and crystallinity (X-c%). It was found that ternary nanocomposite prepared by incorporating 5 wt% of nanoclay and surface treated 1 wt% ZnO to polypropylene had the lowest gas permeability and its oxygen permeability was 24.5% lower than that of pristine polypropylene at 50 degrees C.