A method of manufacturing an organic light-emitting display apparatus includes preparing a lower substrate comprising a display area and a peripheral area surrounding the display area. A first thin film transistors (TFTs) is formed in the display area of the lower substrate. A first insulating layer is formed and disposed in the display area and at least a portion of the peripheral area of the lower substrate and that covers the first TFTs. Organic light-emitting diodes (OLEDs) are formed to be electrically connected to the first TFTs. A barrier layer is formed on at least a portion of the first insulating layer that is formed in the peripheral area of the lower substrate. A sealant is formed on the barrier layer such that at least a portion of the sealant overlaps the first insulating layer, and an upper substrate is sealed with the lower substrate.