Langer's axillary arch is a relatively rare anatomical variation of latissimus dorsi muscle insertion. The clinical importance of this condition in axillary lymph node dissection (ALND) and lymphoedema as well as latissimus dorsi flap reconstruction has been described previously. Axillary vein obstruction in association with this condition has also been reported. We report two cases of Langer's axillary arch encountered during sentinel lymph node (SLN) biopsy which had some bearing on the procedure.