OBJECTIVES: This study estimate the cost-effectiveness of mammography as a screening method for the early detection of breast cancer in women members of a medical insurance company in Antioquia (Colombia). METHODS: A Markov State Model was developed to simulate, from the results of mammographic screening, the diagnosis of breast cancer, five-year survival and the cost of treatment using an initial data set of 4,314 records of women aged 27-89 years who underwent this test between November 2017 and April 2018. The database of mammographic studies was provided by the medical insurance company. The number of Life Years Saved (LYS) was obtained from data on the natural history of the disease at 5 years and the expected response to treatment after cancer detection. The prognosis of the patients depended on the stage distribution of the cancers detected by mammography and the survival rate for each stage. The total costs and health effects associated with the use of mammography were calculated using a modification of the discrete epidemiologic event simulation model for breast cancer in a given population, developed at the University of Wisconsin. Unobservable model parameters controlling natural history and breast cancer detection were estimated through the calibration process to fit age-adjusted specific breast cancer incidence and mortality data reported in Colombia. RESULTS: The evaluation resulted in a total of 742 LYS at a cost of COP $20,233,400.43 (USD $6,996.55) per LYS, which represents 1.1 times the Gross Domestic Product Per Capita (GDP-PC) of Colombia in the same year, so for this study screening mammography is considered a "Cost-Effective" strategy based on the threshold established by the World Health Organization (WHO). CONCLUSIONS: The results obtained suggest that mammography for Colombian women between the ages of 50 and 69 is currently a cost-effective strategy for the Health System, in the early detection of breast cancer.