Grateloupia elliptica has been reported to have the proliferation effect of dermal papilla cells (DPCs), which play important roles in the regulation of hair cycle. In the present study, we examined in vitro and in vivo hair growth-promoting effect of Grateloupia elliptica. When isolated rat vibrissa follicles were treated with extract of G. elliptica, the hair-fiber lengths of the vibrissa follicles significantly increased. Furthermore, the G. elliptica extract accelerated the telogen-angen transition in C57BL/6 mice. To investigate the molecular mechanisms of the G. elliptica extract on the proliferation of DPCs, we examined the activation of wnt/β-catenin signaling which is known to regulate hair follicle development, differentiation and hair growth. The G. elliptica extract activated wnt/β-catenin signaling via the increase of β-catenin and phospho-GSK3β. In addition, the G. elliptica extract increased the level of cyclin E and CDK2, while the level of p27kip1 was decreased. These results suggest that the the G. elliptica extract may induce hair growth by proliferation of DPCs via cell-cycle progression and the activation of Wnt/β-catenin signaling.