Objective: This study aimed to evaluate the efficacy of a national training program in Turkey in improving primary health providers' knowledge and perceived competence about the promotion of early childhood development and prevention, early identification and management of developmental problems; and barriers to implementation and sustainability of skills gained. Methods: A pre-post intervention design was used. Tools measuring perceived competence and knowledge about childhood development were administered to primary health providers before and after training. immediate skills were observed, and implementation and sustainability of skills were determined using individual surveys and focus group discussions I year after training. Results: The training was provided in 5 provinces. Of the 148 primary health providers trained, 90% had >5 years experience in providing primary care. Median knowledge test scores were 13 pretraining and increased to 22 posttraining (p < 0.001). Median perceived competence scores increased from 159 to 222 (p < 0.001). A year after the training, the program and materials were reported to be valued and remembered but used limitedly. Patient load, insufficient time allocated to primary care, lack of reimbursement, and ineffective referrals to pediatricians who had knowledge gaps regarding child development were identified as important barriers to implementation and sustainability of skills gained. Conclusions: in Turkey and potentially other countries with similar health systems, short-term inservice training on child development can improve primary health providers' knowledge, perceived competence and skills related to child development. To decrease the disparities between high- and low- and middle-income countries in addressing child development, significant barriers within health systems need to be identified and addressed.