Background: Children who show disproportionate difficulty with the pragmatic as compared with the structural aspects of language are described as having pragmatic language impairment (PLI) or social communication disorder (SCD). Some children who have PLI also show mild social impairments associated with high-functioning autism or autism spectrum disorder (ASD). There is little robust evidence of effectiveness of speech-language interventions which target the language, pragmatic or social communication needs of these children. Aims: To evaluate the effectiveness of an intensive manualized social communication intervention (SCIP) for children who have PLI with or without features of ASD. Methods & Procedures: In a single-blind RCT design, 88 children with pragmatic and social communication needs aged 5;11-10;8, recruited from UK speech and language therapy services, were randomly assigned in a 2:1 ratio to SCIP or to treatment-as-usual. Children in the SCIP condition received up to 20 sessions of direct intervention from a specialist research speech and language therapist working with supervised assistants. All therapy content and methodology was derived from an intervention manual. A primary outcome measure of structural language and secondary outcome measures of narrative, parent-reported pragmatic functioning and social communication, blind-rated perceptions of conversational competence and teacher-reported ratings of classroom learning skills were taken pre-intervention, immediately post-intervention and at 6-month follow-up. Analysis was by intention to treat. Outcomes & Results: No significant treatment effect was found for the primary outcome measure of structural language ability or for a measure of narrative ability. Significant treatment effects were found for blind-rated perceptions of conversational competence, for parent-reported measures of pragmatic functioning and social communication, and for teacher-reported ratings of classroom learning skills. Conclusions & Implications: There is some evidence of an intervention effect on blind and parent/teacher-reported communication outcomes, but not standardized language assessment outcomes, for 6-11-year-old children who have pragmatic and social communication needs. These findings are discussed in the context of the increasingly central role of service user outcomes in providing evidence for an intervention. The substantial overlap between the presence of PLI and ASD (75%) across the whole cohort suggests that the intervention may also be applicable to some verbally able children with ASD who have pragmatic communication needs. (Contains 6 tables, 2 figures and 3 notes.)