Foliar flavonoids of Nipponanthemum, which is a monotypic genus and consists of only one Japanese endemic species, N. nipponicum, were isolated for the first time. Fifteen flavonoids, i.e. six glycosides, quercetin 3,7-di-O-glucoside, vicenin-2, quercetin 3-O-glucoside, luteolin 7-O-glucoside, kaempferol 3-O-glucoside and apigenin 7-O-glucoside, and nine aglycones, luteolin, nepetin, quercetin 3-methyl ether, axillarin, apigenin, hispidulin, chrysoeriol, jaceosidin and sudachitin were identified. Of these compounds, the flavonoid aglycones existed on the leaf surface.