Mechanical properties of natural rubber composite were improved by adding chitosan nanoparticles in this work. The chitosan nanoparticles were prepared by ionotropic gelation method. The effect of chitosan nanoparticle content in natural rubber at 0, 3, 6 and 9 phr were studied. Size of the synthesized chitosan nanoparticles was 282 ± 96 nm. Natural rubber vulcanization was by electron irradiation at intensity 200 kGy. The morphology of composite was investigated by scanning electron microscopy (SEM). The mechanical properties (tensile strength and modulus) were determined by tensile testing. The interaction of filler-rubber was illustrated by Fourier transform-infrared (FTIR) and dynamic mechanical analysis (DMA). It was found that chitosan nanoparticles was well dispersed within natural rubber matrix. The optimum filler content was affected to mechanicals properties of natural rubber composites. The chitosan nanoparticles at 3 phr in natural rubber composites was found to have the highest mechanical properties. The dispersion and immobilization of chitosan nanoparticles at 3 phr was the best among all loading. In addition, 3 phr chitosan nanoparticles / natural rubber composite had filler-rubber higher interaction than those of other loading.