OBJECTIVE: To compare the different interventions implemented by two groups of parents in the Early Social Interaction (ESI) program and their effectiveness. The intervention lasted nine months. The study was divided into two groups: Individual-ESI (interventionist-single parent, one-on-one instruction) provided home or community-based education 2-3 times per week, and Group-ESI (interventionist-4-5 parents, small group instruction) provided weekly clinic instruction for parents. Parents in both groups were taught how to incorporate appropriate behavior management strategies in their child’s daily life to help their child promote social communication. METHODS: A randomized controlled trial was used. Participants included 82 children aged 16-20 months diagnosed with early-onset autism spectrum disorder. Children were matched according to pre-treatment nonverbal level and each pair was randomly assigned to either Individual-ESI or Group-ESI groups. Child outcomes were assessed at baseline and at the end of the nine-month intervention, including social communication, autism symptoms, adaptive behaviors, and developmental levels. RESULTS: Children in the Individual-ESI group showed significant changes after a psychologist’s standardized observational assessment of social communication, and the Individual-ESI group also showed varying degrees of improvement in parent-reported communication, daily living, and social skills. CONCLUSION: These findings support the facilitating effect of Individual-ESI on children’s recovery outcomes, suggesting the importance of individualized parental coaching in naturalistic settings.