The efficacy of Coelatura aegyptiaca shell powder (CES, 500 mg/kg BW) was evaluated as a calcium supplement in ovariectomized (OVX) rats for ten weeks of treatment. The biochemical components and the antioxidant properties of the shell powder were determined. The bone mineral density (BMD), bone mineral content (BMC), calcium (Ca) and phosphorus (P) contents in serum and bone, serum total alkaline phosphatase (TALP) and bone alkaline phosphatase (BALP), serum calcitonin and parathyroid (PTH) hormones were determined. Furthermore, some of the oxidative stress markers [malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx) and total antioxidant capacity (TAC)] were estimated in bone. The current study revealed that CES contained 19.38% Ca, 0.315% P as well as some of antioxidant amino acids which have a potent antioxidant activity against 1,1-diphenylpicrylhydrazyl (DPPH) free radical. Administration of CES to OVX rats increased BMD, BMC, tibial Ca and P contents and BALP activity, as compared to OVX rats. An ameliorative effect was recorded in the levels of calcitonin, PTH, MDA, SOD, GPx and TAC subsequent to CES administration to OVX rats.This ameliorative effect of CES powder against osteoporosis may be attributed to its antioxidant efficacy and/or to its Ca content. In conclusion, CES may have the potential to develop a clinically useful anti-osteoporotic agent, since its effect was comparable with alendronate (6.5 mg/kg BW/week).