We report the first case of myopericarditis after triple vaccination against diphtheria, tetanus, and poliovirus in a young adult. He presented with fever, acute chest pain, and diffuse ST-segment elevation 2 days after vaccination. Two-dimensional echocardiography findings were normal. Endomyocardial biopsy showed interstitial edema with diapedesis of erythrocytes. Laboratory findings showed inflammatory syndrome and elevated circulating immune complexes. He recovered within a few days with high-dose aspirin treatment and was without complications at 3-month follow-up. We discuss the different hypotheses for infective or hypersensitivity myocarditis.