A thin film transistor substrate includes a data line, a gate line, a gate electrode, a source electrode, a first drain electrode, a semiconductor layer and a second drain electrode. The data line and the gate line cross each other on a base substrate. The gate electrode is electrically connected to the gate line. The source electrode is electrically connected to the data line. The first drain electrode and the source electrode face each other. The semiconductor layer serves as a channel between the source electrode and the first drain electrode. The second drain electrode is disposed on the first drain electrode. The second drain electrode is electrically connected to the first drain electrode.