Sentinel lymph node biopsy has replaced axillary lymph node dissection in those patients with clinically node-negative axilla without compromising their oncologic outcomes. Indication of neoadjuvant chemotherapy has been extended to patients to evaluate the pathologic response and to offer more conservative breast surgery. Sentinel lymph node dissection after neoadjuvant chemotherapy is feasible and accurate in patients with clinically node-negative patients. The timing of the sentinel lymph node biopsy, before or after medical treatment has been studied with benefits for each procedure. Sentinel lymph node dissection has been explored in different randomized prospective studies in clinically positive axilla with the aim of reduce axillary lymph node dissection. However, several studies are necessary to more accurately identify residual axillary disease and the sentinel lymph node after neoadjuvant chemotherapy, to adjust the adjuvant radiotherapy protocols and to evaluate the impact on oncologic outcomes.