This study was conducted to evaluate the effects of Padina arborescens and 1-O-myristoyl-2-O-oleoyl-3-O-(α- D-glucopyranosyl)-glycerol(MOGG), its active component, on the prevention of hair loss. The P. arborescens extract and MOGG inhibited the activity of 5α-reductase, which converts testosterone to dihydrotestosterone(DHT), a main cause of androgenetic alopecia. When immortalized rat vibrissa dermal papilla cells were treated with MOGG, the proliferation of dermal papilla cells significantly increased. In addition, we found that the P. arborescens extract and MOGG could open the K_ATP channel, which may contribute to increase hair growth. Furthermore, MOGG promoted PGE₂ production in HaCaT cells. The results suggest that MOGG from the P. arborescens extract has the potential to treat alopecia via 5α-reductase inhibition, the proliferation of dermal papilla, the opening of the K_ATP channel and/or increase of PGE₂ production.