This study examined whether social exchanges and relationships among young children and with teachers in early care and education are associated with prosocial behavior of children from diverse ethnocultural backgrounds. Social and relational factors including closeness of the teacher-child relationship, emotional tone of teacher-child interaction, engagement in social pretend play, competency in pretend play with peers, and positive social interaction among peers were explored in relation to children's prosocial action. White, African American, and Latino boys and girls who participated in the National Evaluation of Early Head Start were selected for this study just prior to entering kindergarten (N = 1,078). Results indicated that children's engagement in social pretend play and teacher ratings of children's competency in pretend play with peers were associated with the prosocial behavior of children in the three ethnocultural groups. The association of the other social and relational factors with children's prosocial behavior varied across racial or ethnic background. Implications for future research are discussed. (Contains 3 tables.)