The current study investigated associations between early mother-child attachment, as well as mother-child and teacher-child relationships, and internalizing and externalizing behaviors in middle childhood. Data from the NICHD Study of Early Child Care and Youth Development were used. Findings from a series of individual growth curve analyses revealed that attachment security was negatively related to internalizing and externalizing behaviors, while insecure/other and avoidant attachment were positively related to internalizing behaviors. In addition, longitudinal associations were found between mother-child and teacher-child relationships and internalizing and externalizing behaviors across middle childhood. Implications for attachment theory are discussed.