The effects of neutron irradiation on tensile properties of the Cu alloys to type 316 stainless steel (SS316LN-IG) joints fabricated by friction welding method were examined. Additionally, irradiation tests of Al2O3-dispersed copper alloy (Al-25) and SS316LN-IG were conducted. The Al-25/ SS316LN-IG joints were irradiated in the Japan Materials Testing Reactor (JMTR), and tension tests and metallographical observation of these joints have been performed as the post irradiation examination (PIE). In the tension tests of Al-25/SS316LN-IG joints, all irradiated specimens fractured at the copper sides. In the tension tests at 293K, tensile strength of the Al-25/ SS316LN-IG joints irradiated at each temperature was almost similar to that of the base metal (Al-25) irradiated in the same condition. On the other hand, tensile strength of Al-25/ SS316LN-IG joints was smaller than that of Al-25 in the tension tests at the same temperature as each irradiation temperature. In this study, useful data of the irradiated Al-25/ SS316LN-IG joints fabricated by friction welding method were obtained to design fusion reactors.