A young woman presented with takotsubo cardiomyopathy after a syncopal attack caused by torsades de pointes. Two-dimensional echocardiography on admission showed left ventricular apical akinesis (ballooning) and basal hyperkinesis, compatible with takotsubo cardiomyopathy. This gradually normalized in 2 months. ECG on admission showed remarkable QT prolongation, U waves, and negative T waves, which also gradually normalized. Coronary angiography revealed no organic stenosis; however, acetylcholine provocation test caused the QT interval to again become prolonged. During treadmill exercise stress testing, the QT interval shortened as heart rate increased. Therefore, without genetic analysis, this patient was considered to have sporadic long QT syndrome in which takotsubo cardiomyopathy developed after the syncopal attack caused by torsades de pointes.