Most breast operations are categorized as low-morbidity procedures, but a variety of complications can occur in association with diagnostic and multidisciplinary management procedures. Some of these complications are related to the breast itself, and others are associated with axillary staging procedures. This article first addresses some general, nonspecific complications (wound infections, seroma formation, hematoma). It then discusses complications that are specific to particular breast-related procedures: lumpectomy (including both diagnostic open biopsy and breast-conservation therapy for cancer), mastectomy; axillary lymph node dissection, lymphatic mapping/sentinel lymph node biopsy, and reconstruction.