This paper presents our discovery that self-rotation of Melan-a pigment cells can be induced by applying appropriate optical dielectrophoretic (ODEP) parameters. Under optically induced DEP force, which is generated by specific optical electrode patterns and with a band-width of AC bias frequencies, Melan-a cells can be trapped or repelled away from the optical electrodes. In addition, the self-rotation motion of the Melan-a cells was observed. In particular, the applied frequency and voltage dominate the overall cell motion. Hence, the cells can be manipulated on an electrode-free surface. This project studies the rotation and translation motions of the cells in an ODEP system. We speculate that the unbalanced distribution of melanin inside the pigment cells causes this self-rotation phenomenon. Therefore, both pigment cells (Melan-a) and non-pigment cells (Raw 264.7) have been tested in the ODEP experiments to compare their motion behavior. Potential applications for this novel observation are to use the self-rotation phenomenon to elucidate the pigment cells' physical property, and separate the pigment and non-pigment cells.