A patient transfer device includes a base assembly movable in forward and lateral directions. A power train is mounted within the base assembly, and is connected to a clamping and strap assembly. A power and switching system is in electrical communication with the power train. A retractor bar carries one or more clamping devices that are releasably attachable to a sheet. The clamping devices include a clamp handle pivotally connected to a clamp base and a clamp arm eccentrically pivotally connected to the clamp handle. The clamping and strap assembly is supported on the base assembly by a vertical adjustment assembly that includes a positioning mechanism for releasably locking the clamping and strap assembly at one of a plurality of vertical positions. An attendant can stand on the base assembly to act as a counterbalance to a patient's weight.