Transesophageal echocardiography (TEE) can provide real time information about anatomic and hemodynamic state and guide management in cardiac surgery. Despite greater technical advances, TEE has artifacts and pitfalls. This report describes a 68-year-old female patient underwent mitral valve replacement and Maze operation. After the procedures, TEE found right atrial mass which did not exist before cardiopulmonary bypass. After discussing with operator, right atrium was explored because it was thought to be a thrombus attached on pulmonary arterial catheter. However, it was revealed as folding of right atrium. The pitfalls of TEE resulted in misdiagnosis and unnecessary procedure. Therefore, authors reviewed echocardiographical artifacts and pitfalls in right atrium which could be misdiagnosed.