We report a case of right bundle branch block, in which the patient's symptoms and the electrocardiogram findings mimicked those of acute coronary syndrome. In this case report, we stress the significance of apparent ST segment elevation in right bundle branch block. The differential diagnosis is important because right bundle branch block is often complicated with acute coronary syndrome. In addition, right bundle branch block with an ST segment elevation in the specific leads can be a predictor of sudden cardiac death. In such cases, close monitoring of the electrocardiogram findings and careful observation of the patient's symptoms would be necessary.