BACKGROUND: The Society of Surgical Oncology's Choosing Wisely guidelines recommend against routine sentinel lymph node biopsy (SLNB) in clinically node-negative (cN0), hormone receptor (HR)-positive breast cancer patients aged ≥ 70 years. We examined the effect of SLNB on treatment and outcomes in this population. MATERIALS AND METHODS: A single-institution retrospective review of consecutive cN0 women ≥ 70 years of age who received SLNB was performed. We collected clinicopathologic characteristics and treatment data. Patients were compared according to SLN status with subset analysis of HR-positive patients. Outcomes were analyzed using the Kaplan-Meier method and univariable analysis, and were compared using log-rank tests. RESULTS: Of 500 patients, 345 (69%) were SLN-negative. Median age was 74 years (range 70-96). Most tumors were T1 (72%), N0 (69%), invasive ductal (77%), without lymphovascular invasion (88%), estrogen receptor-positive (88%) and progesterone receptor-positive (75%), and human epidermal growth factor receptor 2 (HER2)-negative (88%) treated with lumpectomy (71%). Median number of SLNs obtained was 2 (range 0-12) and median number of positive SLNs was 0 (range 0-8). Characteristics of the HR-positive subset were similar. In both the overall cohort and the HR-positive subset, SLN status significantly affected the use of adjuvant chemotherapy, although no significant effect on recurrence was observed. SLN-negative patients had better overall survival and less distant recurrence (both p < 0.0001). Adjuvant hormone therapy significantly improved overall survival. CONCLUSIONS: SLNB can be safely omitted in elderly patients with T1, HR-positive, invasive ductal carcinoma tumors, but may still provide important information affecting treatment. Patients who are candidates for adjuvant systemic chemotherapy should still be considered for SLNB.