A 37 year-old female patient in whom the transthoracic echocardiography examination revealed dilatation of left heart chambers with left ventricular ejection fraction of 30% and moderate-to-severe mitral valve regurgitation was admitted to our hospital. On 2DTEE examination, mitral valve was normal; however, on 3D images, clefts of both anterior and posterior leaflets were revealed. Isolated cleft mitral valve without any other feature of atrioventricular septal defect is uncommon. 2D echocardiography has limited capability in defining the complex 3D anatomic characteristics of the cleft. 3DTEE allows to visualize the cleft position, morphology, and size, and it is important for surgical planning.