Autism spectrum disorder (ASD) is a neurodevelopmental condition classified based on needs of support, in order to address impairments in the areas of social communication and restricted and repetitive behavior. The aim of this work is to describe the main clinical features of the ASD severity levels in a group of Mexican pediatric patients. The results show firstly that this condition was more frequent in males than females. Secondly, an inverse relationship was found between the intellectual coefficient and the level of severity of the disorder. Thirdly, deficits in social reciprocity and communication were more evident in Level 3, than in Levels 1 and 2, while the difference was less evident in restricted and repetitive patterns of behavior.