Embodiments include a heated underbody support with electrosurgical grounding, such as a heated mattress, heated mattress overlay, or heated pad for supporting a person. The heated underbody support may include a flexible heating element formed of a sheet of conductive or semi-conductive material, a first bus bar along a first edge of the heating element adapted to receive a supply of electrical power, a second bus bar extending along the second edge of the heating element, and a temperature sensor. The heated underbody support may include a layer of compressible material adapted to conform to the person under pressure from the person resting upon the support located beneath the heating element. A water resistant shell may encase the heating element, the first and second bus bars, and the temperature sensor. A return electrode wire may be electrically connected to the flexible heating element to connect to an electrosurgical generator.