The atomistic defect structures of Ni3Al containing C, B and Be atoms were investigated using Debye-Scherrer technique and X-ray diffractometer. It was proposed that the elements of C and B occupy on the interstitial site of the body centered position of the Ll2 structure while the elements of Be substitute on the Al site of the Ll2 structure. Also, it was observed that the additions of C and B atoms into the Ni3Al induced the further ordering of the constituent atoms of Ni and Al. This was more significant at the off-stoichiometric compositions of the Ni3Al. The energetic consideration, involving the nearest neighbor interactions between the constituent atoms, and between the interstitial atom and the constituent atom, was presented in order to explain the further ordering of the constituent atoms.