Transesophageal echocardiography (TEE) is now a common part of intraoperative monitoring in cardiac surgery. Intraoperative TEE offers substantial utility in detection of residual problems requiring reoperation. This report describes a 23 month old patient who was operated on for ventricular septal defect (VSD). TEE following VSD closure revealed a large thrombus in the left atrium (LA). Because of concern about the risk of thromboembolism, the LA was about to be re-explored after TEE demonstration. However, examination by the surgeon as compared with TEE revealed the mass to be an inverted left atrial appendage (LAA) that was easily everted, resulting in the disappearance of this mass on TEE. Echocardiographically, the inverted LAA appears as a mass mimicking a thrombus, a vegetation of the left atrium. Lack of awareness of this entity can result in a misdiagnosis and unnecessary procedures.