OBJECTIVES: To assess the validity of a previously published, updated denosumab budget impact model (BIM), evaluating the budgetary impact to a hypothetical US health plan of increased utilization of denosumab in postmenopausal women with osteoporosis at high risk of fracture METHODS: The BIM was evaluated using face validity, internal validity and cross validity tests. Face validity of the model was assessed by comparing the underlying Markov model with prior published osteoporosis cost-effectiveness studies and osteoporosis reference model. Internal validity was assessed using: 1) extreme value analyses on input parameters; and 2) two-way sensitivity analyses by simultaneously varying the market share, price of denosumab, and direct medical costs of fractures. Cross validity tests were conducted on the following input parameters: population parameters, treatment persistence rate and direct medical costs of fractures. RESULTS: In a base case analysis, increasing utilization of denosumab up to 19.6% of eligible patients in year 3 compared with a constant 16% in years 1 through 3, resulted in a net per-member-per-month (PMPM) of < $0.0025 in each year.  The use of a well-validated osteoporosis Markov model with health states aligned with osteoporosis reference model suggests face validity for the BIM. The results of the BIM model varied in expected directions in internal validity tests: extreme value analysis showed the model was sensitive to the proportion of population currently or newly treated with osteoporosis medication. In the two-way sensitivity analyses, the PMPM increased with increases in price and market share of denosumab. The input parameters used in the model fell within the ranges published in literature, thus providing cross validity. CONCLUSIONS: The current study showed that the denosumab BIM is well validated and can serve as a useful tool to assess the potential impact to a US health plan’s budget of increased denosumab utilization in postmenopausal osteoporosis.