The purpose of the present study was to assess the effects of a professional development program on sixth grade teachers' use of social dynamics management (SDM) practices. SDM practices represent teachers' active attempts to incorporate classroom social dynamics into everyday instructional and behavior management strategies. Sixth grade teachers (n = 17) from two middle schools were randomly assigned to receive the Supporting Early Adolescent Learning and Social Success (SEALS) or to a business-as-usual control condition. Teachers who received the training and consultation provided by SEALS reported more frequent use of SDM practices aimed at managing the general social dynamics of their students and supporting youth who are socially isolated. The latter effect was maintained at a post-intervention follow-up. These results build on a growing body of research on the role of teachers in shaping their students' peer relationships.