We report a case of Takotsubo cardiomyopathy that developed after elective coronary artery bypass grafting (CABG) in an 80-year-old woman. She had been given a diagnosis of unstable angina complicated with mild hypertrophic obstructive cardiomyopathy (HOCM). Her cardiac index began to fall 7 h postoperatively, and we needed to infuse fluids and increase dopamine dose (up to 5 µg/kg/min) to maintain cardiac index and blood pressure. CPK-MB level increased up to 140 IU/l at 12 h postoperatively. Transthoracic echocardiography showed akinesis and ballooning of the apex and hyperkinesis of the base with accelerated left ventricular outflow tract (LVOT) flow and increased mitral regurgitation (MR). Emergency coronary artery angiography showed good patency of all bypass grafts and no new coronary lesion. We diagnosed Takotsubo cardiomyopathy. To improve the hemodynamic status, we started intra-aortic balloon pumping (IABP) instead of adding catecholamines. Blood pressure and cardiac index had improved temporarily, but became unstable again because of increased LVOT pressure gradient and moderate-to-severe MR. LV wall motion gradually improved, but the hemodynamic status stayed unstable, but improved after removal of IABP. In general, the prognosis of Takotsubo cardiomyopathy is favorable with supportive care. However, when it is associated with LVOT stenosis and significant MR, low cardiac output syndrome can become intractable, thus we should manage critical conditions with extreme caution.