<p>This meta-analysis examined the effectiveness of Applied Behavior Analysis-based (ABA) interventions, including Naturalistic Developmental Behavioral Interventions (NDBI), in improving communication, adaptive, and cognitive skills as well as severity of challenging characteristics in children identified as being on the autism spectrum. Furthermore, our investigation extended to the evaluation of potential moderator variables. Twenty-five studies meeting the inclusion criteria were identified. Pre- to post-intervention effects were compared between experimental and control groups. Compared to control-groups ABA-based interventions revealed a large effect size for receptive language skills and moderate effect sizes for adaptive, and cognitive skills. Meta-regression revealed that ABA-based interventions with greater treatment dose and duration yielded greater improvements in adaptive behaviors. Implications for future research and practice are being discussed.</p>