Although existing research has shed much light on the development of ethnic minority children, many studies focus on maladjustment, such as behavioral problems, without also speaking to positive experiences in children's lives, such as friendship. An aspect of development that predicts both positive and negative outcomes for children is self-regulation. The present study investigates precursors and sequelae of self-regulation in middle childhood among low-income, ethnic minority children. The four self-regulatory constructs examined in the current study include low-level executive function (EF; e.g., working memory), high-level EF (e.g., planning), effortful control (EC; e.g., delay of gratification), and impulsivity (e.g., does not think before doing). EC in preschool was related to high-level EF and impulsivity in elementary school. High-level EF explained positive and negative aspects of social development during middle childhood. Additionally, self-regulation during elementary school played a mediating role between EC in preschool and social development in middle childhood.