Disclosed are a thin film transistor, a method of manufacturing the same, and an organic light emitting display device including the same, in which a driving stability of a driving transistor is enhanced even without connecting a source electrode to a bottom gate electrode of the driving transistor. The film transistor includes a N-type semiconductor layer, a P-type semiconductor layer on the N-type semiconductor layer, a first gate electrode on the P-type semiconductor layer, a gate insulation layer between the first gate electrode and the P-type semiconductor layer, a first source electrode connected to a first side of the P-type semiconductor layer, and a first drain electrode connected to a second side of the P-type semiconductor layer.