Boron nitride is a non-oxide ceramic exhibiting excellent thermal and chemical stability. This compound exists in various crystallographic structures, the most common being hexagonal (h-BN) and cubic (c-BN). The surface of this material can be protected from wear by a hard-ceramic compound like aluminum oxide. In this study, aluminum oxide films were deposited on boron nitride substrates by magnetron sputtering. The aim of this work is to evaluate the quality of the interface between these two materials. To do so, the first step was to control the process parameters like the target power, the working pressure and the substrate bias, in order to determine their influence on the deposition rate, on the thin film structure, and on the chemical composition. The use of the two different substrates (h- and c-BN) has also allowed studying the role of the physical and chemical properties of BN substrates on the adhesion of the alumina thin film. The roughness and the surface state of the substrates have been characterized by XPS, optical profilometry, XRD and SEM. It was found that the roughness average of the surface is around 1.48 μm ± 0.12 μm and the elements detected by XPS were boron (37.6 ± 1.3 at.%), nitrogen (47.2 ± 0.9 at.%), oxygen (4.9 ± 0.2 at.%) and carbon (10.3 ± 2.0 at.%). Finally, the role of an annealing treatment on the structural properties of the alumina coating and on its adherence has been investigated. This heat treatment has been performed at 1200°C in vacuum. After annealing, the Al2O3 – BN system has been evaluated using XRD, SEM, XPS, TEM. The interface between the BN substrate and the Al2O3 film was observed by TEM. The corresponding cross section of the h-BN – Al2O3 system clearly shows that there is no interface formation between the substrate and the coating.