Extramedullary plasmacytoma in the anterior mediastinum is very rare. We report FDG PET/CT findings of anterior mediastinum extramedullary plasmacytoma in a 54-year-old woman. On FDG PET/CT, it presented as a solitary anterior mediastinum mass with increased FDG uptake. The final pathology supported a diagnosis of extramedullary plasmacytoma. This case hints us that extramedullary plasmacytoma should be regarded as a differential diagnosis when we encounter a solitary anterior mediastinum mass with intense FDG uptake.