Many cardiovascular disorders may result in blackouts accompanied by abnormal movements attributable to generalized brain hypoxia. In some cases, it may be difficult to distinguish between cardiovascular and epileptogenic causes. Therefore, misdiagnosis of epilepsy and use of unnecessary antiepileptic medication can often be seen in these patients. Although rare in children, atrial fibrillation may cause loss of consciousness. This disorder has strong association with underlying cardiovascular diseases. In this case report, we describe a previously healthy 13-year-old girl presenting with transient loss of consciousness, urinary incontinence, and generalized tonic-clonic convulsions. She was diagnosed with atrial fibrillation based on physical examination and electrocardiography findings. Cardiovascular disorders should be assessed in patients presenting with transient loss of consciousness and seizure-like symptoms. We emphasize that complete physical examination and electrocardiography recording are necessary for correct diagnosis of patients.