Male breast cancer (MBC) is considered as a rare disease that accounts for less than 1% of all breast cancers, and its treatment has been based on the evidence available from female breast cancer. Axillary sentinel lymph node biopsy (SLNB) is now regarded as the standard of care for both female and male patients without clinical and imaging evidence of axillary lymph node metastases, while internal mammary SLNB has rarely been performed. Internal mammary chain metastasis is an independent prognostic predictor. Internal mammary SLNB should be performed to complete nodal staging and guide adjuvant therapy in MBC patients with preoperative lymphoscintigraphic internal mammary chain drainage. We report both axillary and internal mammary SLNB in two cases with MBC. Internal mammary sentinel lymph node did contain metastasis in one case.