In this work, we present a sol–gel method for the preparation of zirconia films. Using zirconium n-propoxide as the starting precursor, a ZrO2 sol has been synthesized that remains stable for several months. Thin films were deposited using the dip-coating method. The structural characterization was performed using waveguide Raman spectroscopy. The films present an amorphous phase up to an annealing temperature of 400 °C. Both monoclinic and tetragonal phases were obtained for annealing temperatures higher than 450 °C. The proportions of these two phases were calculated from the Raman spectra and the size of the crystallites was evaluated using the low-wavenumber Raman band. The optical properties were characterized by the m-lines technique (n = 1.96) and UV–visible spectroscopy. The optical losses for a TE0 mode were measured to be 0.29 ± 0.03 dB cm− 1 for a sample annealed at 400 °C. To optimize the protocol for thermal annealing, a powder obtained from a dried sol was characterized by Thermal Gravimetric Analysis. Rutherford Back Scattering was employed to determine the chemical composition and the stoichiometry of the zirconia films.