Takotsubo cardiomyopathy (TC) is characterized by an acute transient left ventricular systolic dysfunction mimicking acute coronary syndrome (ACS) without significant coronary stenosis. The aim of this study was to examine the electrocardiographic repolarization patterns of TC and ACS and to compare them from hospital admission to hospital discharge. Forty-five patients with TC were matched with 45 patients with ACS according to age, gender, and presence or absence of ST elevation at hospital admission. A complete 12-lead electrocardiography was performed within 12 hours after symptoms onset and then repeated after 3, 5, and 7 days. All patients underwent coronary angiography, and patients with ACS also underwent percutaneous revascularization. Within 12 hours from the symptoms' onset, patients with TC had a significantly fewer number of leads with ST elevation and a significantly more number of leads with T-wave inversion. These differences, however, were not present after 72 hours and a similar trend was seen over time during the 7-day follow-up. Patients with TC had a significant longer corrected QT interval at admission and during the whole follow-up. In conclusion, in the electrocardiograms collected 12 hours within symptoms onset, patients with TC and those with ACS showed significant differences in cardiac repolarization. However, the number of leads with either ST-segment deviation or T-wave alterations in patients with TC soon matched the ACS group undergoing percutaneous revascularization. In contrast, corrected QT interval was persistently longer in patients with TC and, despite a similar reduction in length over time in both groups, it was still significantly longer after 7 days.