Breast cancer is a disease of aging. The average age at diagnosis is 61, and the majority of deaths occur after age 65. Caring for older women with breast cancer is a major challenge, as many have coexisting illness that can preclude optimal breast cancer treatment and which frequently have greater effect than the breast cancer itself. Older patients with cancer should be screened or have a brief geriatric assessment to detect potentially remediable problems not usually assessed by oncologists (e.g., self-care, falls, social support, nutrition). Older women with early-stage breast cancer should be treated initially with surgery unless they have an exceedingly short life expectancy. Primary endocrine therapy should be considered for patients who have hormone receptor-positive tumors and a very short life expectancy, an acute illness that delays surgery, or tumors that need to be downstaged to be resectable. Sentinel node biopsy should be considered for patients in whom it might affect treatment decisions. Breast irradiation after breast-conserving surgery may be omitted for selected older women, especially for those with hormone receptor-positive early-stage breast cancer that are compliant with adjuvant endocrine therapy. The majority of older women with stage I and II breast cancer have hormone receptor-positive, HER2-negative tumors, and endocrine therapy provides them with optimal systemic treatment. If these patients have life expectancies exceeding at least 5 years, they should be considered for genetic assays to determine the potential value of chemotherapy. Partnering care with geriatricians or primary care physicians trained in geriatrics should be considered for all vulnerable and frail older patients.