An exemplary embodiment of the present invention provides a thin film transistor array panel and an organic light emitting diode display including the same including a substrate, a semiconductor disposed on the substrate, a first gate insulation layer disposed on the semiconductor, and a first diffusion barrier layer disposed on the first gate insulation layer. A second diffusion barrier layer is disposed on a lateral surface of the first diffusion barrier layer. A first gate electrode is disposed on the first diffusion barrier layer. A source electrode and a drain electrode are connected to the semiconductor. The first diffusion barrier layer comprises a metal, and the second diffusion barrier layer comprises a metal oxide including the metal.