Background: The aim of this study was to identify the axillopectoral muscle anomaly commonly known as Langer's axillary arch, and to understand its importance in surgical procedures of the axilla. Patients and Methods: Between 2009 and 2011, 758 patients underwent sentinel lymph node biopsy, axillary dissection, or both. Patients with Langer's axillary arch were identified and assessed retrospectively. The decision to cut or preserve the axillary arch was made based on clinical judgment, and patients were followed-up accordingly to monitor for adverse outcomes. Results: Of the 758 patients who underwent axillary procedures, 9 (1.2%) were found to have a Langer's axillary arch. In 2 patients the arch was cut, and in 7 patients it was preserved. No adverse outcomes were identified in any of the patients upon follow-up. Conclusion: Langer's axillary arch is a unique anatomic anomaly of the axillary region that may be problematic due to the potential risks of lymphedema and vascular or nerve compression. It is important for surgeons and radiologists alike to be aware of this anatomic variation in order to properly identify it and respond appropriately based on clinical judgment, and to complete close follow-up of the patient due to the potentially increased risk of adverse outcomes.