OBJECTIVES: Although osteoporotic fractures impose a heavy financial burden on society as a whole, only 20% of patients with osteoporosis and in risk of fracture are being treated. The purpose of this study was to estimate the cost-effectiveness of alendronate therapy for secondary prevention of osteoporotic fractures in Japan. METHODS: A patient-level simulation model with nine health states was developed to predict lifetime costs and quality-adjusted life years (QALYs) of five years of alendronate therapy versus no preventive treatment for Japanese women with osteoporosis, who have a history of hip fracture. Fracture risk associated with age and bone mineral density (BMD) was derived from epidemiologic studies in Japan. We ran the model with different combinations of age (50, 60, and 70), BMD (T-score of −2.5 and −2.0), and BMD-independent fracture risk factors. RESULTS:  For patients with T-score of -2.0 having no additional risk factors, the incremental cost-effectiveness ratio (ICER) of alendronate was $3,023 and $7,389 per QALY gained for those aged 60 and 70 years, respectively. In all other situations, alendronate was dominant over no preventive treatment, with lifetime cost savings ranging from $30,849 to $1,498,961. These results were fairly robust to variations in model parameters. CONCLUSIONS: Alendronate therapy for secondary fracture prevention in Japanese women with osteoporosis provided good value for money.