An organic light-emitting display apparatus includes a thin film transistor including a first insulating layer between an active layer and a gate electrode, and a second insulating layer between the gate electrode and source/drain electrodes, a pad electrode including a first pad layer on a same layer as the source/drain electrodes and a second pad layer, a third insulating layer including an organic insulating material covering the source/drain electrodes and an end portion of the pad electrode, a pixel electrode including a semi-transmissive metal layer, in an opening in the third insulating layer, a cathode contact unit including a first, second, and third contact layers, a fourth insulating layer covering the end portion of the pad electrode, an organic emission layer on the pixel electrode, and an opposing electrode on the organic emission layer.