Lithium salts have been used extensively in both adults and children during the last 30 years, for the treatment of a variety of psychiatric conditions, including bipolar disorder The cardiac side effects of lithium in adult patients have been well described. However, to the best of our knowledge, there are no reports of lithium-induced cardiac side effects in pediatric patients. We describe the case of a 9-year-old boy who developed cardiac toxicity while receiving long-term lithium therapy.