Environmental and internal-hydrogen embrittlements in stress-relieved and recrystallized Ni−16.5Al−8Cr−0.8Hf−0.1B−0.03Y (at. %) have been studied. The stress-relieved Ni3Al-based alloy showed environmental embrittlement when tested in air or in hydrogen gas. The embrittlement is more severe in hydrogen gas than that in air. The recrystallized Ni3Al-based alloy was not susceptible to air, but it was embrittled severely by hydrogen gas and exhibited not only a grain interior but a severer grain boundary embrittlement. When tested in air, the stress-relieved Ni3Al was insensitive to internal hydrogen; however, the recrystallized Ni3Al showed a certain susceptibility to internal hydrogen. With increasing the internal hydrogen content in the alloy, the ductility of the recrystallized Ni3Al decreased steadily and a certain degree of grain boundary embrittlement was observed.