BACKGROUND Podocarpium podocarpum (DC.), an edible and medicinal plant popularly used for the treatment of bruises and fracture in Chinese folk medicine, has been proved to possess significant antiosteoporotic effect in our latest research. PURPOSE Our study aimed to investigate the in vitro and in vivo antiosteoporotic effect of kaempfertrin (KN), a principal flavonoid in P. podocarpum obtained through bio-guided isolation. METHODS An ovariectomized (OVX) rat model of osteoporosis as well as in vitro osteoblast and osteoclast cell lines were employed to evaluate the antiosteoporotic potency of KN. RESULTS KN significantly improved the bone mass and microarchitecture in OVX rats, with little estrogen-like side effect compared with estradiol valerate. KN also exhibited stimulatory effect on osteoblastic cells and inhibitory action on osteoclastic cells, which down-regulated the phosphorylation level of I-κB. CONCLUSION KN possessed significant antiosteoporotic activity. Combined with its limited estrogen-like side effect, KN can be regarded as an idealistic antiosteoporotic candidate for human osteoporosis diseases.