The ginsenoside Rg3, one of active components of red ginseng, has chemopreventive and anti-cancer potential. Cancer stem cells (CSCs) retain self-renewal properties which account for cancer recurrence and resistance to anti-cancer therapy. In our present study, we investigated whether Rg3 as well as the standardized Korean red ginseng extract (RGE) could modulate the manifestation of breast cancer stem-like features through regulation of self-renewal activity.