This pilot study compared the differential impact of two professional development interventions to improve preschool teachers’ use of positive behavioral interventions and supports (PBIS) and decrease young children’s social emotional difficulties. Teachers were randomly assigned to one of two coaching interventions conducted over the course of one academic year. Teachers received either Optimistic Teaching, an approach combining traditional coaching in PBIS with a cognitive-behavioral component to address teachers’ self-efficacy, or traditional PBIS coaching. Teachers in the Optimistic Teaching condition implemented significantly more PBIS skills related to teaching children social skills and involving families in their children’s social emotional development when compared to teachers who were exposed to traditional PBIS coaching alone. Teachers in the Optimistic Teaching condition reported significantly fewer children with serious social emotional difficulties post-intervention. Teachers’ experience and self-reported self-efficacy were analyzed for their influence on teachers’ post-intervention use of PBIS skills. The results are discussed in light of how future professional development efforts might address preschool teachers’ motivation to adopt new practices such as PBIS.