Mechanical properties after neutron irradiation of V-4Cr-4Ti-0.1Si-0.1Al-0.1Y and V-4Cr-4Ti-0.1Si-0.1Al-0.3Y alloys (nominal weight percentage) were studied. Neutron irradiation was carried out at 290°C to 8×10²² n/m² (E>1 MeV, about 0.014 dpa) in the Japan Materials Testing Reactor (JMTR). Tensile tests were carried out using miniaturized specimens at ambient temperature and irradiation temperature. Charpy impact tests were conducted at temperatures from -196 to 0°C using an instrumented machine. There is little difference in tensile properties after neutron irradiation between the two alloys. Increase in yield stress was relatively small (∼100 MPa), and uniform elongation remained more than 10%. Because of a low concentration of interstitial impurities, good tensile properties could be retained even after neutron irradiation at 290°C. Ductile-to-brittle transition temperature (DBTT) of V-4Cr-4Ti-0.1Si-0.1Al-0.1Y alloys hardly changed, whereas absorbed energy was slightly reduced after neutron irradiation.