The interfacial characteristics between thin layers of zirconium dioxide and different thermostable polymers -polyimide, poly(ether ether ketone), and poly(ethylene terephthalate) were studied. These layers, with a thickness ranging from a few nanometers to a few micrometers, were deposited by means of magnetron sputtering from a ZrO2 target. In some cases, the polymers were subjected to plasma treatment (in the presence of different gases: air, Ar, and CO2) prior to ZrO2 deposition. X-ray photoelectron spectroscopy (XPS) analyses indicated clearly that zirconia coatings can be considered uniform when their thickness exceeds c. 10 nm. No interfacial covalent bonds between zirconia and polymers, such as Zr-O-C, were demonstrated. The level of adhesion at the coating-substrate interface was determined by a fragmentation test. The interfacial shear strength, related to the thermodynamic aspects of the polymer surfaces, i.e. their surface energy, was estimated. The result was in good agreement with the existence of physical interactions only, like van der Waals interactions, as shown by the XPS investigation.