Cosmos caudatus (ulam raja) contains high mineral content and possesses high antioxidant activity which may be beneficial in bone disorder such as postmenopausal osteoporosis. The effects of C. caudatus on bone metabolism biomarkers in ovariectomized rats were studied. 48 Sprague-Dawley rats aged three months were divided into 6 groups. One group of rats was sham-operated while the remaining rats were ovariectomized. The ovariectomized rats were further divided into 5 groups: the control, three groups force-fed with C. caudatus at the doses of 100mg/kg, 200mg/kg or 300mg/kg and another group supplemented with calcium 1% ad libitum. Treatments were given 6 days per week for a period of eight weeks. Blood samples were collected twice; before and after treatment. Parameters measured were bone resorbing cytokine; interleukin-1 and the bone biomarkers; osteocalcin and pyridinoline. Serum IL-1 and pyridinoline levels were significantly increased in ovariectomized rats. Supplementation of C. caudatus was able to prevent the increase of IL-1 and pyridinoline in ovariectomized rats. Besides that, C. caudatus showed the same effect as calcium 1% on biochemical parameters of bone metabolism in ovariectomized rats. In conclusion, Cosmos caudatus was as effective as calcium in preventing the increase in bone resorption in ovariectomized rats.