Carbamazepine is a kind of popular drugs which is used in many neurological diseases. The well-known side effects include the dysfunction of hemopoietic systems, severe adverse cutaneous reactions, and abnormal liver function. Cardiovascular abnormality is not uncommon clinically but less mentioned. We introduce an elderly patient who had acute altered mental state after taking carbamazepine and was finally proved to be related to drug-induced cardiac bradyarrhythmia.