Hereditary angioedema (HAE) is a rare genetic disease caused by a deficiency of functional C1 esterase inhibitor that causes swelling attacks in various body tissues. We hereby report a case of out-of-hospital cardiac arrest due to airway obstruction in HAE. Cutaneous swelling and abdominal pain attacks caused by gastrointestinal wall swelling are common symptoms in HAE, whereas laryngeal swelling is rare. Emergency physicians may have few chances to experience cases of life-threatening laryngeal edema resulting in a delay from symptom onset to the diagnosis of HAE. Hereditary angioedema is diagnosed by performing complement blood tests. Because safe and effective treatment options are available for the life-threatening swellings in HAE, the diagnosis potentially reduces the risk of asphyxiation in patients and their blood relatives.