OBJECTIVES:  To examine the economic burden and health care utilization of breast cancer in the US Medicare population. METHODS:  Prevalent cases of breast cancer patients were identified (International Classification of Diseases, 9^th Revision, Clinical Modification diagnosis codes: 174.0, 174.1, 174.2, 174.3, 174.4, 174.5, 174.6, 174.8, 174.9, 175.0, 175.9) using national Medicare data from 01JAN2009-31DEC2013. The first diagnosis date was designated as the index date. Patients were required to have continuous medical and pharmacy benefits 1 year pre- and 1 year post-index date. Study outcomes, including health care utilization and costs, were described in the sample. RESULTS:  Out of 682,543 identified patients diagnosed with breast cancer, 98.23% were women, and 88.64% were white. The mean age of the sample was 76.61 years (standard deviation [SD]=7.27 years) and were more likely to reside in the South US region (38.07%). The average Charlson comorbidity index (CCI) score was 4.25 (SD=3.42). The most frequently diagnosed comorbid conditions included hypertension (72.97%), other malignancies (52.48%), and diabetes (30.09%). Health care resource utilization was encountered in inpatient (24.37%), emergency room (24.17%), physician office (97.75%), outpatient hospital (87.98%), Skilled Nursing Facility (6.93%), Hospice (1.28%), Home Health Agency (15.62%), and Durable Medical Equipment (44.10%) claims. The main costs drivers were inpatient ($5,820), physician office ($6,944), outpatient hospital ($14,039), and Part D pharmacy costs ($2,296), resulting in $33,018 in total health care costs. CONCLUSIONS:  During a 12-month period, Medicare patients diagnosed with breast cancer reported significant health care utilization and costs.