A research-to-practice gap exists in childcare settings, particularly affecting instruction to children with developmental delays (DD) including those with or at risk for autism spectrum disorder (ASD). This study aimed to improve implementation of evidence-based instructional practices by childcare providers in inclusive center-based classrooms; a secondary aim was to examine effects on social and communication outcomes of toddlers with DD and/or ASD. Forty-eight childcare providers from 27 centers and 46 toddlers with social and/or communication delays (mean age = 28.5 months) participated in a cluster-randomized controlled trial. Providers were randomized, at the center level, to Instruction-As-Usual (IAU) or the Early Achievements for Childcare Providers (EA-CP) condition. EA-CP providers received two workshops and weekly, job-embedded coaching. Providers' use of evidence-based instructional practices delivered within a book sharing activity, and toddlers' cognitive, language, and social communication skills were assessed prior to and following training. Significantly greater gains from pre- to post-training in implementation of EA-CP instructional practices were observed in the EA-CP than IAU group (p .001, d = 7.2). Greater social communication gains were observed in toddlers in EA-CP than IAU classrooms (p .001, d = 1.02). Results support the conclusion that the short-term EA-CP professional development program improved implementation of evidence-based instructional practices by childcare providers in inclusive childcare settings, with a direct impact on social and communication outcomes of toddlers with DD, including those with ASD. (author abstract)