Bronchogenic cysts are congenital lesions that are a remnant from abnormal budding of the embryonic foregut. These cysts are usually single; most cases are either asymptomatic or present with respiratory symptoms. A 43-year-old woman presented with intermittent type II atrioventricular block during cholecystectomy. The cardiac evaluation including transthoracic and transesophageal echocardiography and magnetic resonance imaging revealed a cystic homogeneous mass within the interatrial septum. The patient underwent surgical resection of the mass and closure of the septal defect. Histopathology identified ciliated columnar epithelium, consistent with the diagnosis of a bronchogenic cyst.