Nosocomial infections are prevalent complications among patients admitted to intensive care units, with reported incidences ranging from 5% to 10% in Europe and America [1] .These infections result from the overuse of antibiotics, leading to microbial resistance. This project aims to develop biocidal coatings to prevent microbial infections for surface detoxification and ventilation systems. In this context, the development of novel antimicrobial agents based on nanomaterials is currently of great interest in the biomedical field. Metal oxides have emerged as promising candidates [2], notably zinc oxide (ZnO), due to their multifaceted mechanisms in combating bacterial resistance. ZnO garners significant attention as an appealing metal oxide material due to its biocompatibility, easy synthesis and cost-effectiveness [3,4]. In a recent study, we investigated the impact of the size of ZnO nanoparticles (NPs) in suspension on their antimicrobial activity. This investigation prompted us to explore the antimicrobial activity of ZnO NPs thin films. These thin films were synthesized using sol-gel and dip coating methods, with variations in sizes, preferential orientations, and roughness. Subsequently, their impact on antimicrobial activity was examined according to ISO 22196:2011. Our findings revealed that the antibacterial activity of ZnO NPs thin films is enhanced when the films are well-oriented preferentially along the (002) axis and when their size is smaller. Remarkably, these thin films demonstrated robust antibacterial efficacy, even at notably low precursor concentrations of 0.1 M. The main factors influencing the preferential orientation of thin films along the (002) axis and their particle size were identified as the precursor concentration and the length of the carbon chain in the synthesis solvent.