Multilayer barrier films were fabricated by stacking multiple pairs of inorganic and organic layers on organic-treated poly(ethylene terephthalate) (PET) substrates. The inorganic and organic moisture barrier layers were prepared by plasma-enhanced chemical vapor deposition (PECVD) and bar coating, respectively, at room temperature. The water vapor transmission rate (WVTR) through six pairs of inorganic/organic stacking layers can reach 2.1×10-5 g m-2 day-1. By laminating two PET substrates, both coated with two pairs of inorganic/organic barrier layers, individually achieving a WVTR of 5 ×10-3 g m-2 day-1, an ultrahigh-strength moisture barrier film could be produced with the WVTR significantly lowered to as much as 4×10-5 g m-2 day-1, which was in the same order of magnitude as a single PET film coated with six pairs of inorganic/organic stacking layers. Even after bending 5,000 times, the laminated barrier film maintained not only the high moisture barrier strength but also the good optical transparency and flexibility. The possible reason for the significant improvement of the moisture barrier strength by lamination is also proposed.