This work reports on the effect of ultraviolet (UV) laser irradiation on the structural, electrical, and optical properties of nickel oxide (NiOx) thin films, deposited by reactive sputtering of nickel in an oxygen containing atmosphere. It was found that the conduction type can be changed from p-type to n-type and the resistivity decreased as the number of laser pulses is increased and then increases again. The as-deposited films are polycrystalline, while laser irradiation renders the films amorphous. The observed transition from O-rich NiOx as-deposited films to Ni-rich laser-irradiated NiOx can be significant to electrochromic, resistive switching, and other applications. The band gap of the as-deposited and the laser irradiated NiOx films was obtained from spectroscopic ellipsometry measurements and was found to slightly increase upon laser irradiation. It is also observed that the surface roughness increases slightly. Aging effects or instabilities in the structure and composition of the films are also observed under normal conditions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim