OBJECTIVES: This study aimed to model the increase in osteoporosis-related fractures and the associated costs related with aging and testosterone deficiency (TD) in the male population above 65 years in the Brazilian Private Health System (PHS). METHODS: Population-based prospective cohorts established age-specific annual incidence rates of testosterone deficiency and the prevalence of osteoporosis in men. Based on these estimates, projections for the number of cases of men with testosterone deficiency, osteoporosis and fractures in the Brazilian male population above 65 years were computed. The national costs associated with hip fractures have been previously recorded as R$ 24,051 (US$14,402) per event. RESULTS: Among 1,164,379 male individuals above 65 years under the Brazilian PHS, 27,130 new cases of TD would be expected in one year. Considering an osteoporosis incidence of 6% and 12.3% for men with normal and deficient testosterone, respectively, 1709 new cases of osteoporosis attributed to TD would be expected. This would result in an annual absolute increase of 0.16% in non-vertebral fracture incidence in men between 65-69 years; 0.24% between 70-74 years; 0.32% between 75-79 years and 0.40% above 80 years. Each of these absolute increases represents a 105% relative increase in the incidence of non-vertebral fractures between men with TD relative to men without TD. Seventy-one new non-vertebral fractures and 13 new cases of hip fractures would be expected, resulting in incremental costs of R$318,002 (US$190,420) for the Brazilian PHS. CONCLUSIONS: Male aging is associated with gradual decrease in circulating testosterone, which may be detrimental to bone. This model suggests that, for the Brazilian male population above 65 years, testosterone deficiency is associated with a significant increase in new cases of osteoporosis-related fractures in one year.  Diagnosis and proper treatment of this condition could have a favorable impact in the prevention of this costly complication.