An organic TFT array substrate and a fabricating method thereof are disclosed. In the organic TFT array substrate, a data line is disposed on a substrate and a gate line crosses the data line. A source electrode is connected to the data line. A drain electrode is disposed a predetermined distance from the source electrode. An organic semiconductor layer forms a channel between the source electrode and the drain electrode. An organic gate insulating film is disposed on the organic semiconductor layer with the same pattern as the organic semiconductor layer. A gate electrode overlies the organic semiconductor layer on the organic gate insulating film. A gate photo-resist pattern disposed on the gate electrode is used to form the gate electrode. A pixel electrode is connected to the drain electrode.