Access to appropriate early intervention is dependent on timely and accurate identification of children who display early signs of developmental challenges, yet up to 22 % of Australian children have developmental issues that are undetected prior to school. Developmental surveillance using the Social Attention Communication Surveillance- Revised (SACS-R) and the Parents Evaluation of Developmental Status (PEDS) tools was implemented prospectively with a large, diverse sample in community-health and early education settings. Outcomes were investigated to compare the discriminative validity and agreement of the SACS-R and PEDS tools in the early identification of children with Autism Spectrum Disorder (ASD). Results indicate there is a significant difference in the sensitivity and rates of agreement between PEDS and SACS-R in the early identification of ASD across both settings, with SACS-R accurately identifying substantially more children with ASD. Development of policy within health and education sectors that supports implementation of robust, universal developmental surveillance can potentially improve outcomes for children at higher likelihood for ASD.