Osteoporosis is a classical age-related disease that affects women as a consequence of estrogen deficiency. Estrogen deficiency has direct as well as indirect impacts on bone metabolism. Studies revealed that in Myostatin-deficient mice, there is an increase in muscle mass which augments increase in bone strength. The aim of this research is to clarify the effect of myostatin blocking on bone mineral density in ovariectomized rats. Design: 30 healthy adult female albino rats were used to study the effect of myostatin antibodies (injected subcutaneously at a dose of 5 mg/kg daily for 28 days) against osteoporotic effect of estrogen deficiency induced by bilateral ovariectomy. Osteoporotic effect was assessed by analysis of serum levels of myostatin, calcium, phosphorus and concentrations of calcium and phosphorous in femur bone. Results: The results of this study showed that in group II (ovariectomized group), the mean values of serum myostatin and calcium were found to be significantly increased (P< 0.001) when compared with that of group I (control group) with significant decrease in concentration of calcium in femur bone (P< 0.001). Moreover, In group III (ovariectomized / anti-myostatin treated group), the mean values of serum myostatin and calcium were found to be significantly decreased (P< 0.001) with significant increase in concentration of calcium in femur bone (P< 0.001) when compared with that of group II (ovariectomized group). Concentration of phosphorous in femur bone was found to be non significant (P > 0.05) in all studied groups. Conclusions: It was observed that myostatin blockage protects from ovariectomy induced osteoporosis by retaining bone calcium content.