This work studies dependences of resistivity, carrier concentration, mobility and structural properties on the thickness of nickel oxide (NiO) films deposited onto glass substrates by RF magnetron sputtering in a pure oxygen atmosphere at an RF power 200 W. The electrical properties were measured by Hall Effect measurements. The X-ray diffraction (XRD) and transmission electron microscope (TEM) analyses of nickel oxide films indicates that these films are polycrystalline when the samples are prepared with an unheated substrate (T_s=303 K) and using a substrate at a higher substrate temperature (T_s=673 K). The thickness of the films varied in the range from 50 to 300 nm. The variations of the microstructural parameters, such as crystallite size (L), dislocation density (δ), stacking fault probability (α), strain (ε) and density (D), with film thickness and substrate temperature were investigated. The results show the crystallite sizes increaser as the thickness of the film increases. The variation of the dislocation density and the stacking fault probabilities and strain decrease as the thickness increases. The resistivity of NiO film is increased with an increase in film thickness, which is related to the decrease of carrier concentration with film thickness. The NiO film with a thickness of 200 nm has a minimum resistivity of 0.69×10⁻² Ωm when deposited at substrate temperature of 303 K.