Combustion method has been used as a fast and facile method to prepare nanocrystalline Co3O4 spinel employing glycine as a combustion fuel. The products were characterized by thermal analyses (TGA & DTA), X-ray diffraction technique (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) techniques. Experimental results revealed that the molar ratio of fuel/oxidant play an important role in controlling the crystallite size of Co3O4 nanoparticles. Transmission electron microscopy indicated that the crystallite size of Co3O4 nanocrystals were in the range of 14–31 nm. Since the particle size of the powdered samples were found to be equivalent from both TEM and X-ray diffraction technique. X-ray diffraction confirmed the formation of CoO phase with spinel Co3O4. The effect of calcination temperature on crystallite size and morphology has been discussed.