Metal organic chemical vapor deposition (MOCVD) growth of nickel-doped zinc oxide (Ni-doped ZnO) thin films on sapphire is investigated, and structural and optical properties were studied. Samples were grown at two substrate temperatures (450 ℃ and 550 ℃) and at three chamber pressures (22, 30 and 100 Torr). The Ni-doped ZnO samples show (002) hexagonal crystal structure with signs of secondary phases in X-ray diffraction (XRD) measurements. However, different XRD peak intensity were observed for these samples at different growth conditions with same Ni flow rate injection to the reaction chamber. Also, samples grown at different growth conditions have different optical absorption spectra. Results prove that low pressure growth with temperatures close to the decomposition temperatures of the precursors, resulted in optimum dopant incorporation, sharp absorption band edges, and good crystalline quality.