The Ni3Al intermetallic compound with unique properties is widely used especially for high temperature applications such as gas turbines. There are different ways for producing the compound. Among them, high-energy milling technique using a planetary ball mill has been employed for producing nanocrystalline Ni3Al powders. In this research Ni3Al intermetallic was prepared by mixing pure elemental Al and Ni powders. A ball-to-powder weight ratio of 20:1 and rotation speed of 550 rpm in argon atmosphere were considered as the main processing parameters. The milling time ranged from 1 to 55 h. Changes in the phase and microstructure as a function of milling time were investigated using X-ray diffraction analysis and scanning electron microscopy. The results revealed that the formation of nanocrystalline Ni3Al with minimum crystallite size of 5 nm is obtained after 15 h milling. However, further mechanical alloying resulted in increasing grain size. Furthermore, the process efficiency decreased to less than 50% and the lattice strain increased after 55 h mechanical alloying.