BackgroundIn Brazil, large‐scale governmental programmes have been implemented to evaluate the development of all children who are enrolled in public daycare centres and preschools using the Brazilian Ages and Stages Questionnaires: Social–Emotional (ASQ:SE) as a screening tool. However, in the Brazilian context, there is a lack of studies that have investigated the clinical utility of the ASQ:SE, and only a few studies have partially investigated the psychometric properties of the Brazilian version of this scale.ObjectivesThe present study had two aims: (a) to develop reference norms for the ASQ:SE to help professionals screen child development and because the psychometric properties of the ASQ:SE have only been partially examined, (b) to confirm its factorial structure within a multidimensional item response theory framework.MethodsThe sample size was 54,570 children (53% males, 1–5 years old) who were enrolled in Brazilian public daycare centres and preschools and assessed in 2011. The results allowed the development of reference norms for all age intervals by considering raw scores at the 95th percentile as “monitoring zone” and scores at the 99th percentile as “refer child for further evaluation.” Samejima's graded response model was employed, and its fit was checked by the root mean squared error of approximation.ResultsThe results were ≤0.08, indicating sufficient fit for the two‐factor structure. The raw results were 70 and 99.75 (12 months), 75 and 100 (18 months), 70 and 100 (24 months), 85 and 120 (30 months), 90 and 130 (36 months), 95 and 135 (48 months), and 110 and 150 (60 months) for monitoring zone and to refer the child for further evaluation.DiscussionEarly identification is the initial stage in this early identification process, thus allowing for referral or intervention. This study may help identify children with developmental delays.