Abstract Background Sentinel node (SN) biopsy after preoperative chemotherapy (PC) in breast cancer patients is associated with a lower identification rate (IR) and an increased false-negative rate (FNR) compared with SN biopsy in untreated patients. Our aims were to examine the feasibility of SN mapping before PC and the possibility to assess the lymph node status after chemotherapy through a follow-up lymphatic mapping. Methods SN biopsy was performed in 45 clinically node-negative breast cancer patients before PC. A follow-up lymphatic mapping was done after completion of chemotherapy and irrespective of the lymph node status was followed by axillary lymph node dissection (ALND). Results SN mapping before chemotherapy identified a mean of 2.3 SNs in all patients (IR 100%). Nineteen patients revealed a negative SN; 26 patients had a positive SN (micrometastasis found in 6/26 patients). After PC follow-up lymphatic mapping was successful in 29 of 45 patients (IR 64%). IR for follow-up mapping was 80% for patients with a negative or micrometastatic SN before chemotherapy compared with 45% for patients with macrometastatic SNs ( P = .027, Fisher exact test). None of the patients with a negative or micrometastatic SN before chemotherapy revealed positive lymph nodes after PC ( P = .031, McNemar test) and the FNR for follow-up lymphatic mapping in these patients was 0%. Contrary to that, 15 of 20 patients with a macrometastasis before PC had positive nodes after chemotherapy, and the FNR of follow-up mapping in these patients was 50%. Conclusions Patients with a negative SN before PC may forego complete ALND after PC, whereas this may not be valid for patients with macrometastatic SNs. Follow-up lymphatic mapping in patients with positive nodal status before chemotherapy is associated with a low IR and a high FNR.