Objectives <p>Parent-mediated interventions are a core component of services for children with autism and other neurodevelopmental conditions. This study evaluated the feasibility and preliminary effectiveness of the World Health Organization’s Caregiver Skills Training (WHO CST) program in South Korea, including its adaptation to an online, video-based delivery model.</p> Methods <p>A pre-pilot study was conducted between 2018 and 2020 with 50 caregiver–child dyads. During the COVID-19 pandemic, the program transitioned from in-person to synchronous online delivery. In the online format, caregivers practiced intervention strategies in naturalistic home settings and submitted video recordings of caregiver–child interactions. These recordings were reviewed by facilitators to provide individualized feedback during virtual home visits. The core content and structure of the CST program were maintained across delivery formats. Outcomes were assessed using measures of child functioning (WHODAS-C), caregiver knowledge and skills (CKST), and caregiver stress (PSS).</p> Results <p>Significant improvements were observed following the intervention in child functioning, caregiver knowledge and skills, and caregiver stress (all <i>p</i> &lt; .001). No significant differences were found between in-person and online delivery formats, although the online group demonstrated broader improvements across child functional domains. The online CST program implemented from 2020 to 2025 demonstrated strong feasibility, with high retention rates in both in-person (88%) and consistently high caregiver satisfaction (mean scores &gt; 4.5 out of 5).</p> Conclusions <p>These findings suggest that WHO CST can be feasibly and effectively implemented in South Korea, and that online delivery incorporating video-based coaching represents a viable approach for expanding access to caregiver-mediated interventions.</p>