The active fraction of the extract of Asiasari radix, the 60% methanol chromatographic fraction from the ethyl acetate layer (PPAR), was used to investigate the melanogenesis signal pathway in B16F10 melanoma cells. PPAR led to significantly decreased melanin synthesis and tyrosinase activity in a dose-dependent manner. PPAR also reduced the expression of melanogenesis-related proteins including microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase-related protein (TRP)s while down-regulating the expression of mRNA of MITF and tyrosinase. Melanogenesis-regulating signals, such as mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK), phosphatidylinositol 3-kinase (PI3K)/Akt and p38 mitogen-activated protein kinase (MAPK) were evaluated, and ERK was activated by PPAR. The selective inhibitor of MEK/ERK, PD98059, abrogated all suppressive activities of PPAR on melanin biosynthesis, tyrosinase activation and expression of melanogenesis-related proteins. These results suggest that ERK activation by PPAR contributes to reduced melanin synthesis via ERK signal pathway-mediated suppression of MITF and its downstream signal pathway.