A thin film encapsulation (TFE) was fabricated by alternating deposition of organic and inorganic layers via initiated chemical vapor deposition (iCVD) and atomic layer deposition (ALD). A highly crosslinked organosilicone polymer, poly(1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane) (pV3D3) was successfully adopted as the organic layer for the fabrication of TFE. The film formed a stable and smooth interface with ALD Al2O3 layer. The multilayer TFE consisting of pV3D3 and Al2O3 alternating layers exhibited outstanding optical transparency as well as excellent barrier property. Finally, the multilayer TFE was applied monolithically to organic solar cells (OSCs), and the shelf life of the cells was increased immensely, suggesting that the developed organic/inorganic multilayer TFE is an efficient barrier film for elongating the lifetime of organic electronics.