Most mature mediastinal teratomas are not symptomatic until they rupture, and the mechanisms underlying their rupture remain controversial. A 40-year-old woman was admitted to the emergency room with increasing respiratory distress 24 h before admission. Her clinical examination results indicated systemic inflammatory response syndrome with jugular venous distension and bilateral pitting edema on her lower extremity. Thoracic computed tomography confirmed a well-defined anterior mediastinal giant heterogenous mass (22 x 17 x 15 cm) with fluid content that had the same density of pleural effusion. In the culture examination of both sputum and pleural effusion, Streptococcus pneumonia was detected. Surgical findings showed that the tumor contained sebaceous material with some hair and teeth. No teratoma-pulmonary fistula was detected, but oozing through the thin and fragile microscopic hole on the tumor wall was observed. We describe a rare case of a patient with both obstructive and severe septic shock following a ruptured teratoma.