We report a case of thymic cancer with pericardial tamponade in a 70-year-old woman. The patient complained of chest pain and was carried to our hospital. CT scan showed a mediastinal mass and massive pericardial effusion. The effusion was serous fluid, not bloody, and no malignant cells were found. The patient underwent a tumor resection, and the final pathological diagnosis was squamous cell carcinoma of the thymus. In a review of 14 cases of thymic tumor with pericardial tamponade as initial manifestations in the Japanese literature,there were only three cases of thymic cancer. The prognosis was reported to be extremely poor.Some reports showed the effectiveness of chemotherapy and irradiation therapy. We should keep looking for the best treatment for this disease.