The present research presents the results of a cross-sectional study on the relationships among developmental level at the beggining of the first school year, interpersonal relationships, and social abilities at the end of the first school year, in children with and without ASD. The participants were 120 children, 60 diagnosed with ASD and 60 with typical development aged 6 to 7 years, M = 6.27, AS = .20, of which 78 boys (65%) and 42 girls (35%). The instrument used for the measurement of developmental level was Portage Psychomotor Development Scale (Bluma et al., 1976), social skills were measured with 17 items of the Social Skills Rating System (SSRS) (Gresham & Elliott, 1990), and the quality of relationships with others was measured with four items of the Sense of Relatedness Questionnaire (Furrer& Skinner, 2003). Two hierarchical regression analyses were ran, with three steps each. The results showed that child-peer relationship and also child-teacher relationship could diminish the effects of being diagnosed with ASD and also of developmental level on social skills. Practical implications were discussed. Our results support the importance of early interventions for children with ASD as a means to contribute to the developmental level of children with ASD, comparable with children without ASD.