Fish gelatin is a by-product of the agri-food sector, derived from fish processing waste that can be used as or along a packaging material in direct contact with food while maintaining biodegradable properties. The aim of this work was to apply the corona discharge process on fish gelatin hydrogels and to analyse the properties of resulting films after drying. The understanding of changes in the physical or chemical structure of the gelatin layer was focused on at molecular level. Changes in the surface free energy due to corona treatment displayed an increase of the hydrophobicity at highest power tested. Results demonstrated the plasma’s species crossed the gelatin layer and induces weak changes. Indeed, the permeability to various gases was maintained even at high power, confirming that corona discharge systems are suitable devices for treating wet hydrogels without significant degradation of the gelatin layer.