Crinum asiaticum var. japonicum and its active component, norgalanthamine have been reported to have hair growth-promoting effect via the proliferation of dermal papilla cells. In this study, we investigated the other mechanisms of C. asiaticum extract var. japonicum and norgalanthamine on the hair growth. The C. asiaticum var. japonicum extract inhibited 5α-reductase activity by 16%, which converts testosterone to dihydrotestosterone (DHT), a main cause of androgenetic alopecia, whereas the C. asiaticum var. japonicum extract didn`t function as an opener of the K_ATP channel. On the other hand, we examined whether norgalanthamine can inhibit transforming growth factor-β (TGF-β) signal pathway, which is essential in the regression induction of hair growth. Norgalanthamine inhibited the phosphorylation of Smad2/3 on TGF-β1-induced canonical pathway in human keratinocyte HaCaT cells. These results suggested that the C. asiaticum var. japonicum extract and norgalanthamine had the potential to influence hair growth through the inhibition of 5α-reductase activity and TGF-β1-induced canonical pathway.