A multi-energy radiation detector may include an array substrate including a plurality of unit circuits, and/or a photoelectric conversion layer on the array substrate. The photoelectric conversion layer may include a plurality of regions having thicknesses different from each other. A method of manufacturing a multi-energy radiation detector may include forming gate and first electrodes by forming and patterning a first metal layer on a substrate; forming an insulating layer on the gate and first electrodes; forming a channel layer by forming and patterning a semiconductor layer on the insulating layer; forming source, drain, and second electrodes by forming and patterning a second metal layer on the channel layer; forming a passivation layer to cover the source, drain, and second electrodes; forming a first photoelectric conversion layer on the passivation layer; and/or forming a second photoelectric conversion layer on part of the first photoelectric conversion layer.