The effects of aluminum and Y2O3 on the mechanical properties in nano grain Ni-based alloys have been investigated. The test specimens are prepared by mechanical alloying at an Ar atmosphere. The addition of Y2O3 and Al may cause an increase in the tensile strength at room temperature, 400 °C and 600 °C. However, it was confirmed that the increase of tensile strength at room temperature and 400 °C was predominantly caused by addition of Y2O3, while that at 600 °C was mainly due to addition of Al. These results can be attributed to the dispersion strengthening of Y2O3, preventing the formation of Cr2O3 and the change of fracture mode at 600 °C by the addition of Al.