Mediastinum and retroperitoneum are exceedingly rare sites for metastatic prostate cancer to occur. Here, we present the case of a 67-year-old male patient with incidental findings of mediastinal and retroperitoneal masses which were found to be due to metastatic prostate adenocarcinoma based on histopathology and immunohistochemical studies and later on supported by the significantly elevated Prostate Specific Antigen (PSA) levels. Prostate cancer should always be considered in the differential diagnosis of elderly men presenting with metastatic epithelial tumors even in unusual sites.