The aim of the study is to examine the predictive effect of self-regulation on peer relations. Data were collected from 3486 children. Of the study sample, 1736 were girls (49.9%) and 1747 were boys (50.1%). All the children were from high SES families and attending private preschools in 10 cities in Turkey. The results showed that all peer relations variables were statistically significantly correlated with self-regulation skills of the children. Simple linear regressions analyses showed that self-regulation was statistically significant predictor of all peer relation variables (prosocial behaviours, aggressive behaviours, asocial behaviours, exclusion by peers, hyperactivity-distractibility, and fear-anxiety). Self-regulation explains the greatest variation in hyperactivity-distractibility of the children (15%) and the least variation in asocial behaviour (%3). This study shows that self-regulation in early childhood may lead to problems in peer relations. Problems with peers have long-term effects on children's development and mental health. This finding underlines the importance of promoting self-regulation skills in early years.