Background: It is important to find the primary site when axillary nodes metastasis is confirmed after surgery of contralateral breast cancer. Case Report: The authors report a rare case of a 38-year-old female with right occult metastatic breast cancer initially presenting right axillary nodal metastases two years after surgery of left breast cancer. Multifocal cancers were found in all the random pathological sections after right mastectomy, but no abnormalities of the right breast were found even after full examination before surgery. Pathological examination revealed similar findings among the right axillary lymph nodes and the right breast cancer and previous left breast cancer. Six months after right mastectomy, multifocal recurrence was detected in the right parasternal. It was conformed that the right breast cancer was a metastasis from the left. Conclusion: Contralateral breast metastasis should be considered even if no lesion is confirmed when contralateral axillary node metastasis was detected post-breast cancer surgery. Combined axillary lymph node dissection (ALND) and radiation therapy would be an optimal approach, followed by proper systemic therapy.