Zn0.9Mg0.1O nanogranular thin films with a thickness of 250 nm were deposited by sol-gel spin coating process on ITO and glass substrates. Their morphology and microstructure were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and atomic force microscopy (AFM). The surface was dominated by zinc oxide and magnesium carbonates. The electrical properties were governed by capillary condensation. This study demonstrates the sensitivity of these films to humidity and UV light and the interplay between both effects, already observed for individual ZnO nanowires. This highlights the ability of the Zn0.9Mg0.1O thin films to be integrated in humidity and UV sensing devices but with some cautious to allows a separations of the two environmental parameters. (C) 2015 Elsevier B.V. All rights reserved.