A randomized, controlled study was conducted to assess the effects of the Nuestros Ninos professional development program on classroom practices and child outcomes related to language development and early literacy skills in both English and Spanish. Fifty-five teachers and 193 Latino dual language learners (DLLs) enrolled in the North Carolina More at Four Pre-Kindergarten Program participated in the study. The content of the professional development program consisted of research-based instructional practices designed to complement the core curriculum and scaffold learning for DLLs, and the format included professional development institutes, individualized consultation, and community of practice meetings. The results showed that the intervention led to measurable improvements in both the overall quality of teachers' language and literacy practices as well as those specific to working with Latino DLLs, and greater gains in children's phonological awareness skills in their primary language. (Contains 5 tables.)