Mesenchymal chondrosarcoma of the orbit is an extremely rare and aggressive tumor. We report image findings of 18F-fluorodeoxyglucose (FDG) positron emission/computed tomography (PET/CT) in 2 cases, one primary case and one recurrent case. The 18F-FDG PET/CT images revealed high uptake with an SUVmax of 6.7 and 11.7, respectively. In both cases, the HEY1-CoA2 gene fusion was positive. The high uptake of 18F-FDG in mesenchymal chondrosarcoma of the orbit well suggests the malignancy of this tumor.