COVID-19 vaccines have reduced both lethality and hospitalization rates of the novel coronavirus disease. Nevertheless, multiple side effects have been reported in the literature, most often are harmless. We report two cases of acute myocarditis, hospitalized in the emergency department for chest pain occurring after the second dose of mRNA vaccine AstraZeneca. The SARS-Cov-2 infection was ruled out in both patients with a negative PCR obtained by nasal swabs and normal thoracic CT scans. Both patients had high levels of high-sensitive cardiac troponin I. Acute coronary syndromes were excluded with cardiac catheterization. Cardiac Magnetic resonance imaging (MRI) showed signs in favor of acute myocarditis. The evolution was favorable for both patients after being put on anti-inflammatory treatment. The universality and accumulation of reports concerning acute myocarditis following COVID vaccination, in the absence of any other diagnostic element that could explain the myocardial injury, establish a strong causal link, although the etiopathogenesis of such injury remains poorly elucidated.