Carbamazepine is a drug that has been used for a long time to treat various neurological and psychiatric disorders. The drug has effect on many body systems and, in particular, on the cardiovascular. The cardiovascular effect of carbamazepine depends on several factors such as the presence/absence of any comorbidities and its plasma concentration. The drug’s antiarrhythmic effect was demonstrated previously in a number of experimental and clinical studies. In this article, we would like to present the clinical case of pediatric patient with frequent ventricular extrasystoles and arrhythmogenic myocardial dysfunction. Several antiarrhythmic drugs were ineffective in this patient, while carbamazepine administration contributed to the decrease in ectopic activity up to minimal values.