To date, most studies seeking to explore the impact of COVID-19 school closures on student outcomes have focused on cognitive/academic losses. This study explores changes in adaptive behaviors experienced by children and youth with autism spectrum disorders or other developmental disabilities when in-person, one-to-one behavior training was converted to telehealth delivery. Participants in this study were rated on the Adaptive Behavior Assessment System, 3rd Edition (ABAS-3) at three data points: pre-COVID; six months after COVID closure; and 12 months after COVID closure. ABAS-3 standard scores were evaluated to determine any losses or gains in adaptive behavior that occurred during the COVID shutdown of in-person programming. Issues related to assessment of behavior and delivery of telehealth programming are discussed.