The National Early Care and Education Learning Collaboratives (ECELC) project aims to facilitate best practices in nutrition, physical activity, screen time, and breastfeeding support and infant feeding among early care and education (ECE) programs across multiple states. The project uses a train-the-trainer approach with 5, in-person learning-collaborative sessions, technical assistance, and action planning. We describe the longitudinal practice-based evaluation of the project and assess whether ECE programs evaluated (n = 104) sustained changes in policies and practices 1 year after completing the project. The number of best practices increased from pre-assessment to post-assessment (P < .01) but did not change significantly from post-assessment to follow-up assessment. ECELC shows promise as an approach to incorporate professional development and training focused on improving best practices for environment-level child nutrition and physical activity, which is one strategy among many that are warranted for obesity prevention in young children. (author abstract)