A commercial sulfonated polysulfone water treatment membrane was modified by ion beam irradiation. After irradiation, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to identify chemical structure changes incurred by the modification. Some of the sulphonic groups on the surface of the membrane were broken due to ion beam irradiation, which resulted in crosslinking of the polymer. These changes modified the surface morphology of the membrane and also decreased the negative charge of the membrane. Previous studies have determined that ion beam irradiation produces no significant changes in membrane permeability along with improvements in selectivity with respect of organic carbon rejection. Thus, this study focused on conducting bench-scale cross-flow filtration experiments to investigate the cake accumulation on the modified membrane. Through ATR-FTIR and atomic force miscroscopy, it was concluded that fouling of the modified membrane was significantly less severe than that of the virgin membrane. Thus, ion beam irradiation was observed to be an effective membrane modification technique.