CuInS2 powders have been successfully prepared by simple heating a mixture of copper nitrate, indium nitrate and thiourea in ethylene glycol. The prepared powders were fully characterized by SEM, XRD and UV-Vis spectroscopy. The particle shape of the powders obtained with an optimal condition showed spherical shape with about 50 nm in size. The XRD results showed more enhanced crystallized CuInS2 with chalcopyrite structure with increasing reaction time. The values in band-gap energy of nano-sized CuInS2 powders would be estimated 1.63 eV, blue-shifted from that of micron-sized powders due to size quantization effect.