Malignant fibrous histiocytoma (MFH) is the most common soft tissue tumor which often occurs in the extremities and the retroperitoneum. Primary mediastinal MFH is rare; thus, findings on $^{18}F$-fluorodeoxyglucose positron emission tomography/computed tomography ($^{18}F$-FDG PET/CT) of mediastinal MFH have not been reported yet.We report herein the case of a 64-year-old man who was presented with a superior mediastinal mass. The mass showed intense $^{18}F$-FDG uptake with central metabolic defect on PET/CT. The maximum standardized uptake value was 17.4. After tumor removal via median sternotomy, an MFH of the storiform-pleomorphic type was diagnosed on histopathologic examination. We present the first report of $^{18}F$-FDG PET/CT imaging of MFH in the superior mediastinum.