Sudden infant death syndrome (SIDS) is the leading cause of unexpected death in infants under one year of age. Almost all SIDS occurs in infants during sleep, usually without aura, so prevention must take into account its risk factors, including prematurity, fetal alcohol or drug exposure, prenatal or postnatal tobacco exposure, and infection. Breastfeeding is an effective protective factor for SIDS, and several studies have confirmed that it reduces the risk of SIDS regardless of the extent and duration of breastfeeding, with a 45% reduction in partially or briefly breastfed children and a 73% reduction with exclusive breastfeeding, but it is not clear whether breastfeeding can offset the harms associated with other risk factors. Parents should avoid smoking and reduce the use of drugs and alcohol. Timely immunization of infants and family members can also be protective.