A thermal transfer device for providing thermal treatment to a patient. A patient support portion supporting and contacting the patient includes a first segment of a fluid flow path to receive a fluid from a fluid source. A flexible covering coupled and movable relative to the patient support portion defines a space therebetween that substantially conforms to the patient. The flexible covering includes a second segment of the fluid flow path. The fluid is circulated through an inlet, an outlet, and fluid flow path for supplying heat to or removing heat from the patient support portion and the flexible covering. A fluid circulation system with a controller may selectively adjust heat transfer from temperature zones defining the patient support portion. The thermal transfer device or a mattress cover may provide for controlling the microclimate, or conditions at or near the interface between the patient and the patient support portion.