Reactive interlayers consisting of zero valent iron and copper nanoparticles have been successfully incorporated into Surlyn films to fabricate moisture barrier materials with reduced water vapor permeabilities. The reactive nanoparticles dispersed in stearic acid were employed as the interlayers due to their ability to react with moisture. The water vapor transmission rates through the fabricated barrier films with reactive iron and copper interlayers decreased by over 4 orders of magnitude when compared to neat Surlyn. The flexibility and transparency of the barrier films have been evaluated by tensile and UV-visible experiments. Moreover, the accelerated aging studies conducted in accordance with the ISOS-III protocol confirmed the increased lifetimes of the organic photovoltaic (OPV) devices encapsulated with these reactive barrier films. © the Owner Societies 2015.