We conducted a randomized controlled potential efficacy trial to examine effects of two variants of the Tools for Teachers (TfT) professional development (PD) intervention on preschool teachers’ implementation of embedded instruction practices and children’s developmental and learning outcomes. Thirty-six preschool teachers recruited from three school districts were randomly assigned within each district to one of three PD conditions. Preschool children with disabilities (N = 106) from enrolled teachers’ classrooms participated in the study. Results showed that, compared with business-as-usual PD teachers, teachers who received either PD intervention wrote higher-quality learning targets for study children. Teachers who received the PD intervention that included on-site coaching implemented more embedded instruction learning trials compared to teachers in the other two conditions. Compared with children whose teachers participated in BAU PD, children whose teachers received either PD intervention had greater developmental and learning gains as measured by standardized assessments. (author abstract)