In this study, we investigated the effects of the flowers of Lespedeza bicolor on melanogenesis in a mouse melanocyte cell line, B16/F10 cells. Our results show that the flowers of Lespedeza bicolor significantly inhibits melanin synthesis in concentration-dependent manner. In addition, it was also found to inhibit the activity of tyrosinase, the rate-limiting melanogenic enzyme. While the flowers of Lespedeza bicolor have no direct inhibitory effect on tyrosinase activity in cell free assay system using mushroom tyrosinase. Moreover, the flowers of Lespedeza bicolor effectively suppressed the ${alpha}-MSH-stimulated$ melanin formation, tyrosinase activity and dendrite outgrowth. These results suggest that the flowers of Lespedeza bicolor is a potent depigmetation agent.