Proton conduction at the interface between a perfluorosulfonic acid (PFSA) electrolyte membrane and a platinum electrode has been modified using a radiation-chemical reaction technique with gamma-rays. For room temperature, the proton conductivity at the interface for the gamma-ray irradiated membranes is enhanced by approximately two orders of magnitude as compared to that of the unirradiated membrane. In addition, the radiation-induced significant change in hydrophobicity is observed in the near-surface regions of the irradiated membrane using a water contact angle. The improvement of the water uptaken characteristics due to the presence of some intrinsic defects such as peroxy free radicals and fluorocarbon radicals, produced by radiolysis, leads to the enhancement of the proton conductivity.