Mesenchymal chondrosarcoma of paranasal sinuses is a rare malignant tumor arising in skeletal and extraskeletal sites. Histologically, a combinaton of celluar zones composed of undifferentiated small cells and chondroid zones typically presents a bimorphic appearance that is virtually pathognomonic in most cases. Ablative surgical treatment seems to be the procedure of choice and the value of irradiation or chemotherapy is still under debate. Prognosis is usually poor, and long-term follow up is necessary. The authors experienced a case of mesenchymal chondrosarcoma of paranasal sinuses which occurred in 19 years old male who underwent external ethmoidectomy, left and is free of local recurrence or metastasis on up-to-date follow-up.