Organic electronic devices such as organic light-emitting diodes (OLEDs), quantum dot LEDs, and organic photovoltaics are promising technologies for future electronics. However, achieving long-term stability of organic-based optoelectronic devices has been regarded as a crucial problem to be solved. In this work, a simple and reproducible fabrication method for ultralow water permeation barrier films having a triple-layered (triad) hydrogenated silicon nitride (a-SiN x :H)/nanosilicon oxynitride (n-SiO x N y )/hybrid silicon oxide (h-SiO x ) multistructure is presented. Two triad (a-SiN x :H/n-SiO x N y /h-SiO x ) n=2 multistructure barrier films are deposited on both sides of a poly­(ethylene terephthalate) substrate using a combination of low-pressure plasma-enhanced chemical vapor deposition and dip coating. The deposited films show a high average transmittance (400–700 nm) of 84% and an ultralow water vapor transmission rate of 2 × 10–6 g/m2/day. In the electroluminescence characteristics of OLEDs encapsulated with two triad barrier films, the operational lifetime (T 50) of OLEDs is 1584 h, which is almost similar to that (1416 h) of OLEDs encapsulated with a glass lid.