In a mental rotation task of objects, typically, reaction time (RT) increases and the rotation related negativity (RRN) increases in amplitude with increasing angles of rotation. However, in a mental rotation task of hands, different RT profiles can be observed for outward and inward rotated hands. In the present study, we examined the neurophysiological correlates of these asymmetries in the RT profiles. We used a mental rotation task with stimuli of left and right hands. In line with previous studies, the behavioral results showed a linear increase in RT for outward rotations, but not for inward rotations as a function of angular disparity. Importantly, the ERP results revealed an RRN for outward rotated stimuli, but not for inward rotated stimuli. This is the first study to show that the behaviorally observed differences in a mental rotation task of hands is also reflected at the neurophysiological level.