A method of reducing fuel vapor permeation through a multi-layer tank includes providing a multi-layer overlay onto at least a portion of a structural layer of the multi-layer tank. The multi-layer overlay preferably comprises at least one structural layer composed of a polymeric material that is compatible with one or more of the polymeric structural layer(s) of the multi-layer tank. The multi-layer overlay further comprises at least one barrier layer composed of a vapor barrier material resistant to hydrocarbon permeation therethrough. The multi-layer overlay may be secured to the multi-layer tank by, for example, applying a suitable amount of heat and pressure thereto or by molding the multi-layer overlay to the tank body during a tank forming process.