We investigated whether ethanol extracts of the safflower seeds containing phenolic compounds were responsible for the bone-protecting effects. Crude ethanol extract (CEE) of the safflower seeds was fed for 4 weeks at the level of 1% in diet to female Sprague-Dawley rats that had been subjected to bilateral ovariectomy (OVX). The CEE effects (OVX+CEE) were evaluated by comparing results obtained from OVX, Sham, and OVX injected with $17{eta}$-estradiol ($OVX+E_2$) groups. OVX resulted in a dramatic reduction in the trabecular bone mass of the proximal tibia (approximately 40% of the Sham group) and an increase in fat deposition in bone marrow. In $OVX+E_2$ group, the bone loss was completely prevented as well as marrow adiposity. In OVX+CEE group, approximately 80% of the bone mass was maintained compared with Sham group and fat deposition in the bone marrow was prevented. Meanwhile, the partially purified ethanol extract containing the phenolic compounds stimulated proliferation of the ROS 17/2.8 osteoblast-like cells in a dose-dependent manner, as potently as positive controls of $E_2$ and genistein. The present data demonstrate that the ethanol extracts of safflower seeds reduced bone loss caused by estrogen deficiency. The bone-protecting effect of safflower seeds seems to be mediated, at least partly, by the stimulating effect of the phenolic compounds on the growth of osteoblasts.