This systematic review and meta-analysis aimed to identify and evaluate the quality of randomised controlled trials (RCTs), assessing the efficacy of Social Skills Group Programs (SSGPs) for primary and secondary school aged autistic children and adolescents exploring the influence of informant, setting characteristics and teaching strategies as moderating factors for social outcomes. A search of the electronic databases of Medline, ProQuest, CINAHL, Scopus, and Web of Sciences electronic databases was conducted for the period January 1, 2013 until December 31, 2023 for peer-reviewed RCT studies published in English, evaluating the efficacy of SSGPs for school-aged autistic children and adolescents (6-18 years). Included studies were assessed for methodological quality and efficacy using random effect meta-analysis. Informant analysis and moderator analyses were also conducted investigating the influence of informant, setting characteristics and teaching strategy utilised in the SSGPs on the participants social outcomes. Sixty-five studies were included in the systematic review with 49 studies included in the meta-analysis. Although most studies had strong or good methodological quality, a high possibility of publication bias was detected in the meta-analysis. After statistical adjustments for publication bias were made, findings revealed that SSGPs had no effect on the overall outcomes assessed by included studies on school-aged autistic children and adolescents. However, informant analysis revealed small effects reported by self-report, parent-proxy and researchers. Teaching strategies and setting characteristics were not significant moderators for the efficacy of SSGPs on the social outcomes of autistic children and adolescents. This review highlights the need for improvements in measurement frameworks for assessing social skills in autistic children and adolescents.