The important research direction in surface engineering and photovoltaics is the development of new materials that can replace the previously used expensive films. A prospective compound is zinc oxide (ZnO), characterized by optical and electrical properties similar to ITO and a lower production cost. One of the key factors influencing the properties of the ZnO thin films is the technique and parameters of their production. The comprehensive investigation results of the influence of ZnO thin-films deposition process temperature on their structure, optical properties, and adhesion are presented in the paper. ZnO films were deposited by the magnetron sputtering method. The structural characteristics of the tested films were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffractometry (XRD) and Raman spectroscopy, while the optical properties of the films were studied by the UV/VIS spectroscopy. Thickness and adhesion measurements of the obtained films were performed using the spectroscopic ellipsometry technique and the scratch test, respectively. The obtained research results showed the influence of the deposition process temperature on the morphology, crystallite size and adhesion of the thin films to the substrate. The effect of process temperature on optical properties, the value of the optical bandgap and crystal structures were analyzed and described. The results of this work have a meaning for the development of surface engineering and may serve as a clue in future studies in the field of modern photovoltaic structures.