Acute myocarditis is inflammation of the myocardium most often following a viral infection. Its diagnosis is one of the most difficult to make with certainty in cardiology, due to the lack of specificity of the clinical presentation, ECG and ultrasound changes, and the restrictive use of myocardial biopsy (BM). For these reasons, we report the case of a 22-year-old athlete who presented with severe chest pain. Cardiac MRI allows direct characterization of myocardial damage; different diagnostic sequences make it possible to locate areas of inflammation, edema, and necrosis, and the distribution of lesions in the muscle makes it possible to distinguish between ischemic and inflammatory damage.