We herein report a rare case of collision lymph node metastases of breast and thyroid carcinomas. A 49-year-old female had undergone an extensively radical mastectomy of the right breast for inflammatory breast cancer at our hospital. Eleven months later, she presented with enlarged lymph nodes in her right lateral neck and multiple nodules in bilateral thyroid lobes. The patient underwent total thyroidectomy and radical dissection of the bilateral cervical lymph nodes. A histological examination showed multiple foci of papillary thyroid carcinoma (PTC) in the bilateral lobes. Surprisingly, concurrent metastases of breast carcinoma and PTC were shown in one of the lymph nodes from the right jugular region. This rare case of collision metastasis and the related literature are discussed.