Abstract: The present invention relates to a self-aligned organic thin film transistor (TFT) and a fabrication method thereof. According to the present invention, a gate electrode is formed from a first conductive layer patterned on a substrate, a gate dielectric layer is formed on top of the substrate to cover the gate electrode, and a second conductive layer is then formed on the gate dielectric layer. Subsequently, ultraviolet (UV) backside exposure for irradiating the second conductive layer with UV from a bottom side of the substrate using the gate electrode as a mask, and source/drain electrodes self-aligned with the gate electrode is then formed not to overlap with the gate electrode by developing the second conductive electrode. Thereafter, an organic semiconductor layer is formed between and on the source/drain electrodes. In the present invention, an organic TFT can be fabricated using a reel-to-reel process, and therefore, the fabrication process can be simplified.