Tin (Sn) is a candidate material for anodes (negative electrodes) of lithium-ion batteries because of its high theoretical energy capacity. In this paper, we report an observation of Sn-whisker growth on Sn-thin films after lithiation and delithiation. The compressive stress generated by electrochemical lithiation of the Sn-thin films is likely the driving force for the growth of the Sn whiskers. Attention should therefore be paid to the issue of Sn-whisker growth for Sn-based electrodes since Sn whiskers may penetrate through the separator, and short-circuit the electrochemical cell.