Ruta graveolens L. has been widely used to treat various skin ailments, especially vitiligo. In this study, we isolated a new furanocoumarin named Rutagrarin (1) along with 14 known compounds (2-15) from the aerial parts of R. graveolens and elucidated their chemical structures via various spectroscopy. We found that compound 5 promoted melanogenesis and tyrosinase activity in B16 cells. Further investigation on underlying mechanisms revealed that compound 5 activated the transcription of microtia-related transcription factors and promoted the production of melanin in B16 cells via the Akt/GSK-3 beta/beta-catenin pathway. Therefore, we confirmed the traditional efficacy of R. graveolens and speculated that compound 5 could be used as a natural drug to treat vitiligo.