A thin-film transistor substrate and a display apparatus including the same includes a first thin-film transistor on a substrate. The first thin-film transistor includes a first semiconductor layer having a first channel area, a first source area, and a first drain area; a first lower gate electrode between the substrate and the first semiconductor layer; a first upper gate electrode on the first semiconductor layer and overlapping the first channel area; and a first electrode layer on the first upper gate electrode and electrically connected to at least one of the first source area and the first drain area. The first lower gate electrode overlaps the first channel area and the first drain area.