A majority of children’s language learning experiences occur in inclusive early child care and education settings. Few evidence-based professional development (PD) programs exist to empower early childhood education providers to use language instruction practices with children in inclusive classrooms. There is little research on providers’ implementation of naturalistic developmental behavioral intervention (NDBI) strategies to improve children’s language outcomes in whole-group inclusive instruction. We conducted a pilot cluster randomized controlled trial to test the hypothesis that providers in the Early Achievements for Child Care Providers (EA-CP) PD program would show greater gains in NDBI implementation fidelity during shared book reading relative to business-as-usual (BAU) providers. This hypothesis was confirmed. Compared to BAU providers, EA-CP providers exhibited significantly greater fidelity gains from pre-training to mid-training, post-training, and 12-week maintenance assessments. A secondary hypothesis was that toddlers with and without developmental delays in the EA-CP condition would exhibit greater vocabulary and communication gains than toddlers in the BAU condition. Analyses of children with and without delays showed significantly greater expressive vocabulary and story-related engagement and communication in the EA-CP group. For children with delays, positive effects favoring the EA-CP group but not statistically significant were found. Implications for research, practice, and policy are discussed. (author abstract)