This paper presents a 4-DOF-exoskeleton mechanism for nervous system injury rehabilitation of the wrist and hand. The mechanism has three motors for the wrist and one for hand actuation. The 3-DOF wrist rehabilitation mechanism implements motions including flexion, extension, ulnar and radial deviation as well as pronation and supination. The hand opening and closing motions are implemented by the 1-DOF hand rehabilitation mechanism. This 4-DOF exoskeleton mechanism is designed to be attachable to the shoulderelbow rehabilitation robot to make a full-DOF system for upper limb rehabilitation.