Decreased production of the mucin MUC5AC in the eye is related to several pathological conditions, including dry eye syndrome. A specific strategy for increasing the ocular levels of MUC5AC is not yet available. Using a plasmid specially designed to encode human MUC5AC, we evaluated the ability of hybrid cationized gelatin nanoparticles (NPs) containing polyanions (chondroitin sulfate or dextran sulfate) to transfect ocular epithelial cells. NPs were developed using the ionic gelation technique and characterized by a small size (<200 nm), positive zeta potential (+20/+30 mV), and high plasmid association efficiency (>95%). MUC5AC mRNA and protein were detected in conjunctival cells after in vitro transfection of the NPs. The in vivo administration of the NPs resulted in significantly higher MUC5AC expression in the conjunctiva compared to untreated control and naked plasmid. These results provide a proof-of-concept that these NPs are effective vehicles for gene therapy and candidates for restoring the MUC5AC concentration in the ocular surface.