Organic light-emitting display apparatus

An organic light-emitting display apparatus includes a thin film transistor comprising an active layer, a gate electrode, a source electrode, a drain electrode, a first insulating layer between the active layer and the gate electrode, and a second insulating layer between the gate electrode and the source and drain electrodes, a pad electrode comprising a first pad layer at a same layer as the source electrode and the drain electrode and a second pad layer on the first pad layer, a third insulating layer covering the source electrode and the drain electrode and an end portion of the pad electrode, a pixel electrode comprising a semi-transmissive electrically conductive layer in an opening in the third insulating layer, a protection layer between the pixel electrode and the first insulating layer, a fourth insulating layer having an opening in a location corresponding to the opening formed in the third insulating layer, the fourth insulating layer covering the end portion of the pad electrode, an emission layer on the pixel electrode, and an opposing electrode on the emission layer.