An organic light emitting display includes a gate electrode on a substrate, an active layer insulated from the gate electrode, source and drain electrodes that are insulated from the gate electrode and contact the active layer, an insulating layer between the active layer and the source and drain electrodes, a light blocking layer that is on the active layer and that blocks light of a predetermined wavelength from the active layer, and an organic light emitting device that is electrically connected to one of the source and drain electrodes.