A patient, with severe chest pain and isolated ST segment elevation, was evaluated in order to differentiate ischemic heart disease, such as acute myocardial infarction. A fishhook was incidentally found during coronary angiography, chest CT and esophagoscopy. With this information, the patient was re-interviewed, and it was learned that the patient had swallowed the fishhook from cooked fish after fishing trip. The patient was diagnosed as traumatic acute pericarditis with acute mediastinitis, associated with esophageal and pericardial perforation. The patient was successfully treated by surgical treatment drainage and adequate antibiotic use. We report a case of traumatic acute pericarditis, which mimicked an acute myocardial infarction, with a review of the literature.