A case of lymphoepithelioma-like carcinoma of the mediastinum is reported. A 67-year-old male was admitted to Tokyo Medical College Hospital, in February of 1992, for evaluation of an abnormal mediastinal shadow on chest X-ray. The mediastinal tumor was biopsied using mediastinoscopy. Histological diagnosis was undifferentiated carcinoma and radiation therapy was performed. Six months after treatment, he complained of dyspnea. Combination chemotherapy was performed. Although the tumor size decreased, he died of pneumonia. Histological findings at autopsy included nesting of large carcinoma cells with vacuolar nuclei and large nucleoli, interstitial lymphocytic infiltration similar to that of lymphoepithelioma of the epipharynx, and lymphoepithelioma-like carcinoma in the thymus. The epipharynx and thymus were, however, intact at autopsy. We found no other origins of this tumor, including the trachea and lung. This case was therefore diagnosed as lymphoepithelioma-like carcinoma of the mediastinum.