A nanoparticle barrier-coated substrate is prepared by mixing pigment nanoparticles, a binder and a liquid carrier to form a coating solution, applying the coating solution onto the substrate and drying the coating solution to form the barrier coating on the substrate. The pigment nanoparticles can be chosen from talc, calcium carbonate, clay, silica and plastic and the substrate can be a cellulosic material or an inorganic material. If the substrate is initially provided with large pores, a precoating can be applied to the substrate prior to the application of the pigment nanoparticles thereto.