A sample of 341 5 1/2-year-old children participating in an ongoing longitudinal study was the focus of a study on the relation between cardiac vagal regulation and peer status. To assess cardiac vagal regulation, resting measures of respiratory sinus arrhythmia (RSA) and RSA change (suppression) to 3 cognitively and emotionally challenging tasks were derived. Results indicated that vagal regulation was positively associated with peer status. In addition, mediational analyses revealed that the relation between vagal regulation and peer status was mediated through better social skills for girls and better social skills and fewer behavior problems for boys. These findings are discussed in terms of the role of vagal regulation in the facilitation of children's positive social behavior.