Nickel oxide (NiO) has been considered widely as an electrochemical capacitor or supercapacitor electrode material. NiO thin films are successfully deposited at various substrate temperatures. Influence of substrate temperature on various physical and electrochemical properties has been studied. X-ray diffraction analysis confirms cubic phase of polycrystalline nickel oxide. SEM images show porous surface having inhomogeneous randomly shaped heaps. Optical band gap energy is found to be in the range of 3.04–3.28eV. Electrical resistivity confirms the semiconducting behavior of NiO with room temperature activation energies 0.30–0.38eV. Electrochemical characterization is carried out by testing the NiO electrodes for cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Specific capacitance of 405Fg−1 at the scan rate of 5mVs−1 is observed. Galvanostatic charge-discharge study confirmed the pseudocapacitive nature. Furthermore, the specific capacitance of the NiO can still keep a good retention of 92.10% after 1000cycles at 1Ag−1, demonstrating the outstanding long-term electrochemical stability. This work offers useful reference for supercapacitor applications in the future.