An organic thin film transistor and a method for fabricating the same are disclosed. The method for fabricating the organic thin film transistor includes forming a gate electrode on a substrate. A gate insulating layer is formed on an entire surface of the substrate including the gate electrode, and source and drain electrodes are formed at a predetermined interval from each other on the gate insulating layer. An organic semiconductor layer is formed on the entire surface of the substrate and a first protection layer is formed on the organic semiconductor layer. The first protection layer is patterned and the organic semiconductor layer etched using the remaining first protection layer as a mask. A second protection layer is then formed on the entire surface of the substrate.