Research Findings: Children's social competence has been linked to successful transition to formal school. The purpose of this study was to examine the contributions of children's temperament to teachers' ratings of their social competence from kindergarten through 2nd grade. Children (N = 1,364) from the National Institute of Child Health and Human Development Early Child Care Research Network participated in this study. Mothers rated children's shyness, attentional focusing, and inhibitory control with the Children's Behavior Questionnaire at 4 1/2 years, and teachers rated children's social competence with three subscales (cooperation, assertion, and self-control) of the Social Skills Rating System at kindergarten, 1st, and 2nd grade. Latent growth curve analysis indicated that both shyness and effortful control contributed to children's social competence. Bolder children were likely to have higher assertion ratings, and shyer children with greater attentional focusing were likely to have higher assertion ratings. Shyer children and children with greater inhibitory control and attentional focusing were likely to have higher teacher ratings of self-control and cooperation. Practice or Policy: Findings highlight the importance of considering child temperament characteristics when understanding children's social competence and successful adjustment to kindergarten. Information may help parents, preschool teachers, and early elementary teachers prepare children who may be at particular risk for lower social competence. (Contains 3 tables and 1 figure.)