We describe here a case with a large bronchogenic cyst treated by surgical resection, who presented with evidence of left atrial overload on electrocardiogram (ECG). The 50-year-old male patient presented with the chief complaint of heaviness in the chest on exertion. An ECG revealed evidence of left atrial overload, and echocardiography and imaging revealed a mass having a maximum diameter of 9 cm on the cranial aspect of the left atrium, caudal to the tracheal bifurcation. The patient was treated by surgical resection of the cystic mass via right anterolateral thoracotomy. His postoperative course was satisfactory and the patient was relieved of his main symptom.