ABSTRACTBiocomposites of waste polypropylene (WPP) with bagasse fiber as reinforcing component can be readily prepared based on waste management application. Bagasse was subjected to chemical treatments using sodium hydroxide (NaOH) and vinyl triethoxysilane to modify the fiber properties. Scanning electron microscope and Fourier-transform infrared spectroscopy were used to elucidate fiber modification after treatments. Compounding of WPP at various ratios of bagasse was produced by melt mixing. Treated and untreated fiber composites were investigated under conditions of gamma irradiation at 20 kGy. In general behavior, at different fiber loadings, treated biocomposites have better properties than untreated one and fiber treated with silane is the best. Furthermore, treated biocomposites represented more biodegradability under soil than untreated one. The results of mechanical properties showed that the as-prepared fiber composites have superior irradiation-resistant properties.