Epoxy nanocomposite spray-coatings containing large aspect ratio modified graphene (MG) were successfully prepared in a facile manner. The individually exfoliated MG nanosheets form liquid crystalline mesophases in the epoxy precursor at low loadings. The epoxy/MG nanocomposite films exhibit significantly improved gas barrier properties even in humid conditions. The spray-coating method allows for the preparation of high MG content nanocomposites in large scale without compromising processability. Implication of the present finding for fabrication of high-performance graphene-based packaging films with multi-functionality is discussed.