Provided are a sensor array substrate and a method of fabricating the same. The sensor array substrate includes: a substrate in which a switching element region and a sensor region that senses light are defined; a first semiconductor layer which is formed in the sensor region; a first gate electrode which is formed on the first semiconductor layer and overlaps the first semiconductor layer; a second gate electrode which is formed in the switching element region; a second semiconductor layer which is formed on the second gate electrode and overlaps the second gate electrode; and a light-blocking pattern which is formed on the second semiconductor layer and overlaps the second semiconductor layer, wherein the first semiconductor layer and the second semiconductor layer are disposed on different layers, and the second gate electrode and the light-blocking pattern are electrically connected to each other.