Radiation-induced graft copolymerization of alpha methyl styrene (AMS)-butyl acrylate (BA) mixture onto poly(etheretherketone) (PEEK) was carried out to produce copolymer films which were subsequently sulfonated to develop proton exchange membranes. The characterization of membranes was carried out with infrared spectroscopy (FTIR), differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction analysis (XRD), contact angle and electron probe microanalysis (EPMA). The presence of sulfonic acid groups within the polymer matrix was confirmed by FTIR. The crystallinity of membranes decreased significantly upon sulfonation process. The melting temperature of the membranes also decreased as compared to the virgin and the grafted films. At the same time, glass transition temperature (T (g)) of membranes increased as the grafting increased. Virgin film showed stable thermogram up to similar to 500 A degrees C while the grafted film had two-step degradation pattern. Sulfonation introduced one additional decomposition range in the membrane. Contact angle images showed the hydrophilic nature of the membrane surface. The EPMA showed the presence of the sulphur across the membrane matrix in a homogenous manner. The membranes showed low resistivity of 62 Omega cm for the graft level of 27 %.