Organic light-emitting devices (OLED) are extremely sensitive to moisture and oxygen. Without high-performance hermetic seals, the life of these devices is limited. Bottom-emitter OLEDs are commonly sealed using epoxy and cover glass with large amounts of desiccant. In top-emitter OLEDs the light passes through the cover glass on which the desiccant typically resides. Thus, transparent thin-film encapsulation without any desiccant is most desirable. This paper reports the results of a robust thin-film encapsulation method that utilizes a layer of aluminum oxide deposited by atomic layer deposition (ALD) process as the primary moisture barrier. More than 1000 h in 85 °C and 85% RH testing has been observed without significant device degradation caused by moisture. Data corroborating this method's superiority over other physical deposition methods for OLED encapsulation are also presented.