A thin film transistor (TFT) substrate, an organic light-emitting display apparatus including the TFT substrate, and a method of manufacturing the TFT substrate that enable simple manufacturing processes and a decrease in the interference between a capacitor and other interconnections are disclosed. The TFT substrate may include a substrate, a TFT arranged on the substrate, the TFT including an active layer, a gate electrode, a source electrode, and a drain electrode, a pixel electrode electrically connected to one of the source electrode and the drain electrode, and a capacitor including a lower capacitor electrode and an upper capacitor electrode, the lower capacitor electrode formed from the same material as the active layer and arranged on the same layer as the active layer, and the upper capacitor electrode formed from the same material as the pixel electrode.