In this work, the electrochromic and structural properties of NiO thin films prepared using optimized low value electrodeposition parameters were studied. The optimized parameters were deposition current density, molar concentration of nickel nitrate solution, and deposited charge density. The highest electrochromic characteristics corresponded to deposition parameters of -0.05 mA/cm2 deposition current density, 0.02 M of Ni(NO3)2.6H2O solution, and charge density of 80 mC/cm2. For this optimized film, at 630 nm wavelength, the transmittance modulation ΔT was 76 %, the efficiency η was 19 cm2/C, the charge reversibility Qc/Qa was 97%, and a remarkable contrast ratio CR of 5.9. In addition, a good cycling stability was confirmed up to 900 cycles. Optimized NiO thin films were poorly crystallized exhibiting a nano-flake structure, high porosity, and homogeneity.