The present study examined the role of language capacities in explaining differences in social information processing (SIP) among three school-age groups: high-functioning children with autism spectrum disorder (ASD, IQ > 75), children with specific learning disorder (SLD), and children with typical development (TD). Participants were 96 boys in Grades 3 to 6, comprising 25 boys with ASD, 38 with SLD, and 33 with TD. SIP measures included two peer vignettes (group entry, ambiguous provocation) to highlight influences of social context. Both clinical groups (SLD, ASD) differed significantly from the nonclinical (TD) group in total language capacities and in five of six SIP measures. As hypothesized, language capacities also significantly mediated the two disorders' associations with children's deficits along SIP stages. Findings from this novel comparative study call for consideration of semantic-pragmatic language's role when planning interventions that target social cognition in both clinical populations as well as further empirical exploration.