Pure and Nickel oxide doped chromium (III) oxide (Cr2O3) nanoparticals are synthesized by hydrothermal technique. The effect of dopant Ni concentration on the structural behavior of Cr2O3 nanoparticles was examined by X-ray diffraction. The average crystallite size of the synthesized nanoparticles was measured from XRD patterns using Scherrer equation and was decreased from 22nm to 12.9 nm with the increasing Nio concentration in Cr2O3 from (0, 0.01, 0.06, and 0.10). Morphologies and compositional elements of the synthesized nanoparticles were observed by the field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) spectroscopy, respectively. The optical property of the samples was measured by ultraviolet - visi...