Secondary tumours of the thyroid gland account for 1.25 to 3 % in clinical series and reach 24 % in autopsy series. Chondrosarcoma is a rare malignant mesenchymal tumour of chondrogenic nature; the mesenchymal variant represents less than 3 % of all chondrosarcomas, being therefore extremely rare. A mesenchymal chondrosarcoma metastasis in the thyroid is exceptional; to our knowledge, only three previous cases of chondrosarcoma metastasis in the thyroid have been reported to date but none of such cases corresponded to a mesenchymal chondrosarcoma. We present the first of such a case in a 27-year-old woman with a 4-year history of mesenchymal chondrosarcoma of the sacrum that was treated by surgery and chemotherapy. At the present admission, head and neck computed tomography revealed a well-defined nodule in the thyroid gland. The diagnosis of metastasis from the mesenchymal chondrosarcoma was made in the right lobectomy specimen.