Perinatal asphyxia is an important cause of neonatal morbidity and mortality. Hypothermia is an effective treatment of neonatal hypoxic-ischemic encephalopathy in infants. Cold agglutination is a primary or acquired autoimmune disease that involves autoantibodies that lead to hemagglutination at low temperatures lower than that of the body. In this case the importance of cold agglutinins during therapeutic hypothermia is presented.