An organic light emitting display having a small thickness and a fabrication method thereof are provided. The organic light emitting display includes a substrate, an non-transmissive layer formed on the substrate, a semiconductor layer formed on the non-transmissive layer, a gate insulation layer formed on the semiconductor layer, a gate electrode formed on the gate insulation layer, an inter-layer dielectric layer formed on the gate electrode, a source/drain electrode formed on the inter-layer dielectric layer, an insulation layer formed on the source/drain electrode, and an organic light emitting diode formed on the insulation layer.