Fiber-textured and epitaxial NiO thin films were deposited on Si(100), c-Al₂O₃, and muscovite mica(001) sub-strates using reactive magnetron sputtering at substrate temperatures of 300 °C and 400 °C, to investigate theeffect of film thickness and substrate temperature on epitaxial growth of NiO films. The as-deposited filmsexhibited a face-centered cubic structure with a larger lattice constant, attributed to strain induced during thesputtering process. With an increase in substrate temperature to 400 °C, the d-spacing decreased due to strainrelease, approaching the NiO bulk value for the thickest film. The NiO film grown on Si(100) displayed fibertexture. On c-plane sapphire, NiO thin films exhibited twin domains and three-fold symmetry, consistent withexpected crystallographic orientation relationship for NaCl-structured materials onsapphire: (111)_NiO ‖ (0001)_Al2O3 and [011]_NiO ‖ [1010]_Al2O3, [011]_NiO ‖[1010]_Al2O3. On muscovite mica(001)substrates, the observed epitaxial shows that the mechanism is conventional epitaxy, rather than van der Waalsepitaxy, consistent with the epitaxial growth of the non-layered non-van-der-Waals compound NiO. The epitaxialrelationship was identified as of (111)_NiO‖(001)_Mica and [011]_NiO ‖[010]_Mica, [011]_NiO ‖[010]_Mica.