The onset mechanism of takotsubo cardiomyopathy is unkown. The reported cases of takotsubo cardiomyopathy that happened after cardiac surgical operation were very few. We describe one case of takotsubo cardiomyopathy with left ventricular outflow tract obstruction (LVOTO) that occurred after having undergone mitral valve replacement (MVR) for combined valvular disease. The patient was an 82-year-old woman who was hospitalized with congestive heart failure in our hospital. She had diagnosis of rheumatic valvular disease (i.e. severe mitral regurgitation and mild mitral stenosis, secondary tricuspid regurgitation), atrial fibrillation and pulmonary hypertension. She had a sigmoid septum pointed out by cardiac ultrasonography. Preoperative coronary angiography was normal. After general anesthesia induction, bradycardia and hypotension developed. Therefore epinephrine and norepinephrine were administered. The rheumatic mitral valve was replaced using a 27 mm-size mitral pericardial bioprosthesis, preserving the posterior mitral leaflet. DeVega tricuspid annuloplasty and maze surgery were also performed at the same time. We did not recognize wall motion abnormalities by the transesophageal echocardiographic examination during the operation. On postoperative day 1, she was extubated and became hypotensive immediately. Takotsubo cardiomyopathy was diagnosed from characteristic views (an apical ballooning and a preserved basal contraction of the left ventricle) by transthoracic echocardiography (TTE). This echocardiogram showed also LVOTO of pressure gradient 38 mmHg. Blood transfusion and discontinuation of epinephrine infusion improved LVOTO. TTE showed a gradual recovery of the left ventricle to normal systolic function, on postoperative day 34. The postoperative coronary angiogram was normal. We presumed that LVOTO was important in the onset and severity of takotsubo cardiomyopathy. In this report, we showed also the pathological significance of the sigmoid septum.