Commotio cordis is a rare phenomenon when ventricular fibrillation and sudden death occurs with a blunt, nonpenetrating blow to the chest. Individual susceptibility to commotio cordis has been demonstrated in swine models, and might be present in humans as well. We report a case of commotio cordis in an adolescent with a heterozygous mutation on the gene CACNA1C, encoding for an L‐type calcium channel expressed in the heart. This genetic mutation has been previously associated with a phenotype of long‐QT syndrome; however, this was not demonstrated in our patient despite extensive investigations. To the best of our knowledge, this is the first report of commotio cordis in which an ion‐channel gene mutation involved in repolarization abnormalities has been documented. This finding might corroborate the hypothesis that a genetic predisposition plays a role in the individual susceptibility to this rare cause of cardiac arrest.