A number of studies of parent-mediated interventions in autism spectrum disorder have been published in the last 15 years. We reviewed 19 randomized clinical trials of parent-mediated interventions for children with autism spectrum disorder between the ages of 1 and 6 years and conducted a meta-analysis on their efficacy. Meta-analysis outcomes were autism spectrum disorder symptom severity, socialization, communication-language, and cognition. Quality of evidence was rated as moderate for autism spectrum disorder symptom severity, communication-language, and cognition, and very low for socialization. Weighted Hedges' g varied from 0.18 (communication-language) to 0.27 (socialization) and averaged 0.23 across domains. We also examined the relationship between outcome and dose of parent training, type of control group, and type of informant (parent and clinician). Outcomes were not significantly different based on dose of treatment. Comparing parent training to treatment-as-usual did not result in significantly different treatment effects than when parent training was compared to an active comparison group. Based on parent report only, treatment effects were significant for communication-language and non-significant for socialization, yet the opposite was found based on clinician-rated tools. This meta-analysis suggests that while most outcome domains of parent-delivered intervention are associated with small effects, the quality of research is improving.