The goal of this study was to provide Head Start teachers with specific skills in developing positive relationships with students and in more effectively managing problematic child behavior in the classroom. The hypothesis was that teacher behavior management training (BMT) would reduce child problem behavior and create a more supportive social environment in Head Start classrooms compared to standard teacher practices, or treatment as usual (TAU). Ten teachers serving twenty classrooms in three centers received six hours of specialized training in addition to training as usual, while seven teachers serving fourteen classrooms in two centers received training as usual. Training as usual consisted of standard teacher training provided by Head Start. BMT entailed the addition of 6 hours of group teacher training grounded in “The Incredible Years: Promoting Positive Academic and Social Behaviors” approach, and individualized in-class mentoring. Repeated measures ANOVAs (group X time) were used to assess group differences in change in children’s behavior from fall to spring of the school year. There was a significant group X time interaction (p = .013) in observed rates of child disruptive and aggressive behavior which increased over time in the TAU group and decreased in BMT group.