We examined the role of the teacher-child relationship quality (close, dependent, and conflictive) on preschoolers' (N=95) academic readiness for kindergarten, and we tested children's prosocial and aggressive behavior and peer group exclusion as mediators of this relation. A unique feature of this study is the ethnically and socio-economically diverse preschool-aged sample. The association between close teacher-child relationships and academic readiness was partially mediated by prosocial behavior and peer group exclusion. There was also evidence of a transactional association between close teacher-child relationships and children's behavior. Additionally, children's behavior and peer group exclusion mediated the relation between negative teacher-child relationships (dependent and conflictive) and academic readiness. The findings suggest that teacher training, education, and support for establishing close teacher-child relationships may maximize preschoolers' academic readiness by promoting social adaptation.