In one embodiment, an organic light emitting diode (OLED) display is provided. The OLED display includes a substrate, a first signal line formed on the substrate, a second signal line intersecting the first signal line, a first thin film transistor connected to the first and second signal lines, a second thin film transistor connected to the first thin film transistor, a first electrode connected to the second thin film transistor, a second electrode provided at least partially opposite to the first electrode, and a light emitting member formed between the first electrode and the second electrode, wherein at least one of the first thin film transistor and the second thin film transistor includes a plurality of semiconductor layers having different crystallinity.