Absence of the pericardium is a rare congenital disease in which the fibroserum membrane covering the heart is partially or totally absent. It is characterized by few echocardiography (ECG) and imaging features that can mislead the diagnosis to an inherited cardiac disease, such as arrhythmogenic right ventricular cardiomyopathy. Although it has often a benign course, this congenital defect should be identified as in some cases herniation and strangulation can be life-threatening and cause sudden cardiac death. Red flags on ECG (sinus bradycardia, variable T-wave inversion), chest x-ray (Snoopy sign, absence of tracheal deviation, and esophagus impression), and transthoracic echocardiogram (unusual windows, teardrop left ventricle, and elongated atria) should rise the suspicion of pericardium absence. The correct diagnosis, confirmed by cardiac magnetic resonance, is mandatory as the consequences on the sport activity certification, the management, and the treatment are extremely different.