Various encapsulating films for flexible organic light-emitting diodes (OLEDs) were studied,and gas barrier layers including inorganic Al2O3 thin films prepared by atomic layer deposition,organic Parylene C thin films prepared by chemical vapor deposition, and their combination wereconsidered. The transmittance and water vapor transmission rate (WVTR) of the encapsulatingfilms were tested. The effects of various encapsulating films on the luminance and currentdensity of the OLEDs were compared. Lifetime experiments on OLEDs with these encapsulatingfilms were also conducted. The results showed that the transmittance is acceptable even if thepolyethylene terephthalate (PET) substrates were coated with two Al2O3 and Parylene C layers. Theresults also indicated the WVTR of the PET substrate was improved by coating the barrier layers.Evaluation of the performance after encapsulation indicates that the OLEDs with Al2O3/PET,Parylene C/Al2O3/PET (1 pair/PET), and Parylene C/Al2O3/Parylene C/Al2O3/PET (2 pairs/PET)presented similarly higher luminance compared with the other two cases. Although the 1 pair/PETencapsulation behaved slightly better in terms of luminance than the 2 pair/PET encapsulation, the2 pairs/PET encapsulation has much longer lifetime. The OLED with 2 pairs/PET encapsulationhad nearly double the lifetime compared with the 1 pair encapsulation, and four times comparedwith the OLED without encapsulation.