Langer's axillary arch (AA), the most common anatomical variant in the axillary area of definite clinical significance. This is an updated review of the reported variations in the structure, highlighting its morphological diversity and its potential in complicating axillary lymph node biopsy, lymphadenectomy, or breast reconstruction. A review of the literature concerning the AA published between 1812 and 2020 was performed using the PubMed, Scopus, Embase, and Cochrane medical databases. The frequency, laterality, morphology, origin, lateral attachment points, vascularization, and neurosis of the AA were the parameters retrieved from the collected data. The prevalence of AA ranged from 0.8% to 37.5%. It is more often unilateral, muscular in nature, and extending from the latissimus dorsi to the pectoralis major. It is vascularized by the lateral thoracic vessels or the subscapular artery and innervated by the thoracodorsal nerve. Langer's AA, when present, may complicate surgical procedures in the area; therefore, every surgeon performing breast or axillary surgery should be aware of this entity and its variations to ensure maximal effectiveness and safety in the management of patients.