This study was conducted to evaluate the effect of Grateloupia elliptica, a seaweed native to Jeju Island, Korea, on the prevention of hair loss. When immortalized rat vibrissa dermal papilla cells were treated with extract of G. elliptica, the proliferation of dermal papilla cells significantly increased. In addition, the G. elliptica extract significantly inhibited the activity of $5{alpha}$-reductase, which converts testosterone to dihydrotestosterone (DHT), a main cause of androgenetic alopecia. On the other hand, the G. elliptica extract promoted $PGE_2$ production in HaCaT cells in a dose-dependent manner. The G. elliptica extract exhibited particularly high inhibitory effect on LPS-stimulated IL-12, IL-6, and TNF-${alpha}$ production in lipopolysaccharide (LPS)-stimulated bone marrow-derived dendritic cells. The G. elliptica extract also showed inhibitory activity against Pityrosporum ovale, a main cause of dandruff. These results suggest that G. elliptica extract has the potential to treat alopecia via the proliferation of dermal papilla, $5{alpha}$-reductase inhibition, increase of $PGE_2$ production, decrease of LPS-stimulated pro-inflammatory cytokines and inhibitory activity against Pityrosporum ovale.