We reported a case of mediastinal bronchogenic cyst in a patient with a high serum level of CA19-9. The patient, a 41-year-old man, presented with a complaint of persistent fever. Chest X-ray examination, computed tomography and magnetic resonance imaging showed a subcarinal mass shadow which was diagnosed preoperatively as a bronchogenic cyst. The serum level of CA19-9 was 73 U/ml. The cyst was partially removed via right thoracotomy. Histopathological findings were compatible with bronchogenic cyst. The CA19-9 level in the specimen was 134,00 U/ml. The serum level of CA19-9 decreased to normal postoperatively. The postoperative course was uneventful.