Essential oils (EO) are complex mixtures of natural molecules with a great activity against bacteria, virus and fungi. Despite their wide use in folk medicine, their employment in medicine or in biomedical products is still scarce and there are only few studies in literature. Their antibacterial and anti-adhesive properties are of interest for the development of coatings or functionalization of implant surfaces, but also for non-implantable medical devices, with the advantage of a reduced bacterial contamination, without the risk of developing bacteria resistance. For a first attempt, a peppermint essential oil was used in this research. The aim of the work was to functionalize or to coat the surface of different materials (Ti6Al4V, Steel 316L) with different surface finishing (grinded, polished, and chemically-treated). The obtained samples were characterized by means of XPS, FTIR, Fluorescent microscope observations and tape test. These analyses highlighted the presence of grafted oil biomolecules, or of a coating, on all the substrates after the procedure of functionalization/coating with remarkable chemical stability (during soaking in water or washing with acid or basic solutions) and mechanical adhesion. The samples were also subjected to antibacterial tests selected in order to simulate non-implantable applications: the test showed a reduction of the adherent bacteria and their viability on coated surfaces. In conclusion, the research work shows the great potential of the use of essential oils for surface functionalization or coating of biomaterials to obtain enhanced antibacterial properties: according to the final application, different oils can be selected in order to obtain the desired effects.