When placed in an outdoor environment, organic electronic devices (OEDs) can degrade on exposure to moisture, UV light, and heat, owing to the chemical sensitivity and decomposition of the organic materials. Therefore, to protect OEDs from outdoor environments, thin-film passivation, which can block harmful elements from reaching organic materials, is required. To meet the demands and trends in encapsulation technologies, in this study, we developed a low-temperature, simple, and effective gas diffusion multibarrier (GDM), which is UV and heat reflective as well as corrosion resistant. The designed UV- and heat-reflective GDM (UHGDM) has a multistacked structure in the form of a UV filter/Ag/gas diffusion barrier (GDB)/polymer based on a dielectric/metal/dielectric (DMD) configuration. First, the DMD structure was used as a heat mirror for infrared reflectance. Second, the bottom dielectric layer of the DMD structure was used as the UV filter, and it consisted of a ZnS/LiF multistacked structure with large differences in refractive indexes. Third, a nanolaminate-based GDB barrier with multi-interfacial and defect-decoupling systems, which achieved a water vapor transmission rate of 1.58 x 10(-5) g/m(2)/day at a thickness of 60 nm, was used as the top dielectric layer of the DMD structure. Finally, an inorganic/organic hybrid polymer layer was coated on the DMD structure to provide corrosion-resistance and waterproofing properties. The fabricated UHGDM showed high transparency in the visible region and excellent reflectance in the UV and IR regions, resulting in excellent UV and heat rejection capability in practical UV and heat reflection tests. In addition to optical functionalities, the UHGDM maintained its functionality against harsh environmental conditions because of the GDB/polymer structure. Finally, the feasibility of the UHGDM was demonstrated using organic solar cells through water immersion and shelf lifetime tests.