A sample of 496 early childhood teachers was assigned randomly in two phases to a series of professional development (PD) interventions. Phase I intervention was a 14-week course on effective teacher-child interactions. Participants were then re-randomized into Phase II intervention, which consisted of individual, interactions-focused coaching. Impacts of the course, coaching, and their combination were evaluated relative to business-as-usual controls on knowledge of effective interactions, skill in detecting effective interactions, observed teacher-child interactions, beliefs about intentional teaching, and children's classroom engagement. "Research Findings:" Teachers exposed to the course demonstrated greater knowledge of and skills in detecting effective teacher child-interactions, and displayed higher quality instructional support in their interactions with children during the year following the course. Teachers who received coaching were also observed to display higher levels of instructional support and children in their classrooms displayed more positive engagement with adults. However, neither teachers nor children appeared to gain additional benefit from the combination of the course and coaching. "Practice or Policy:" The results have important implications for efforts to systematically and efficiently improve the quality of early childhood programs through the delivery of PD that is directly aligned with teachers' classroom interactions.