AbstractHerein, we prepared functional chitosan films reinforced with chitin nanocrystals by supercritical solvent impregnation with a variety of essential oils, i.e. mentha, clove, and cinnamon. Two different chitosan film structures were evaluated, smooth and compact films obtained by casting; and highly porous films prepared by lyophilization process. The effect of the film morphology, essential oil impregnation and the presence of chitin nanowhiskers on the properties of the films were extensively investigated by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and tensile testing; while the bioactive functions were evaluated by measuring the antioxidant and antimicrobial activities. It was found that the impregnation of essential oils is much higher in porous films, confering notable antioxidant and antimicrobial activity. The incorporation of chitin nanocrystal does not influence on the impregnation process, and only improves slightly the antioxidant performance, which is clearly appreciable in the case of films obtained by casting with an increase of ca. 35% from chitosan without to samples with 5 wt% of chitin nanowhiskers. Nevertheless, an important enhancement of the mechanical properties, particularly in elastic modulus, is clearly appreciated with the incorporation of chitin nanowhisker into the films, with values of 50% higher in comparison with chitosan without nanowishers. However, the elongation at break and tensile strength values suffer a slight decrease. Graphical Abstract