Primary germ cell tumors of the mediastinum are rare, accounting 1-5% among all germ cell tumors and 10% of all neoplasms in this area. Approximately 85% of these tumors occur in men with a mean age 29 years. These tumors are mainly found in the anterior mediastinum and appear grossly as large lobulated masses. They are frequently invasive at the time of diagnosis and almost 90% of patients are symptomatic. Primary nonseminomatous germ cell tumor arising in the posterior mediastinum is very rare. We report a case of 37- year old male arising from the posterior mediastinum. Serum tumors markers including alpha-fetoprotein and beta-hCG which are usually elevated in germ cell tumor were not elevated. He was found to have a primary mediastinal embryonal carcinoma with pulmonary metastasis at open exploration. He was treated with debulking surgery and cisplatin-based chemotherapy, died of sepsis after 15 months postoperatively.