The present study aims to evaluate the results of the Applied Behavior Analysis (ABA) intervention in children with Autism Spectrum Disorder (ASD) in the city of Rio de Janeiro. ASD is a neurodevelopmental disorder marked by social communication deficits and restricted, repetitive behaviors. Specifically, this study investigates developments in the areas of socialization, cognition, language, and motor development, assessed using the Operationalized Portage Inventory (IPO). Twenty children participated in the research: thirteen boys and seven girls between two and six years old. Data collection was divided into three stages: an initial interview with parents, application of the inventory before the intervention, and reapplication of the same inventory after twelve months of intervention. Our results show that the ABA intervention was effective in the area of socialization. Furthermore, the data indicate that the language area showed the lowest performance both before and after the intervention period. This research adds to the body of evidence for the use of ABA interventions as a therapeutic tool in the treatment of children with ASD. Continued research in Rio de Janeiro and its surroundings is important to monitor progress in the treatment of ASD both locally and nationally.