Introduction. The systematic assessment of child development in the first years of life is an essential component of pediatric health checkups. The Ages and Stages Questionnaire, third edition (ASQ-3) is the most validated scale, and has been recommended by the UNICEF to verify if children have a normal neurological development. It is a monitoring instrument to assess the main developmental areas, including communication, gross motor, fine motor, personal-social, and problem solving skills, and to compare the local population to the international development standards. Objective. To validate the ASQ-3 in a pediatric population group. Methods. Children aged 1-66 months were assessed at a public hospital by pediatricians, psychologists, and educational psychologists. The SSPS software package was used to determine population scales. Results. In 630 children, who had a homogeneous sex distribution, an 88% sensibility and a 94% specificity were determined, with a positive predictive value of 88% and a negative predictive value of 96%, compared to the National Screening Test (Prueba Nacional de Pesquisa, PRUNAPE) and the cut-off scores for each age group. Conclusion. The ASQ-3 established that 19.5% of children were at risk of experiencing neurodevelopmental disorders. The ASQ-3 met psychometric properties compared to the PRUNAPE, which is the gold standard for the targeted and systematic assessment of developmental milestones during health checkups in a rapid, simple and cost-effective manner, so it was considered useful to monitor child neurological development.