A rare case of chondroblastic osteosarcoma arising from the ethmoid sinus is reported. The patient, a 34-year-old woman, presented with diminished visual acuity of the left eye. CT and MR imaging showed a heterogeneous left-sided nasoethmoidal mass destroying the medial orbital wall. Biopsy revealed a chondroblastic osteosarcoma containing malignant chondroid elements and calcified malignant osteoid. Treatment consisted of craniofacial resection followed by radiotherapy and chemotherapy with symptomatic improvement. We briefly discuss ethmoidal osteosarcomas.