While laboratory and school playground-based independent evaluator (IE) rated measures of intervention outcome have been used in some clinical trials for autistic individuals (Dawson Pediatrics 125:e17–e23, 2010), IE ratings of children’s behavior in their home environments are virtually nonexistent in published clinical trials in autism. In the present study, IE-rated measure of children’s social isolation in the home setting pre and post intervention is utilized to evaluate treatment effects from a cognitive behavioral therapy (CBT) treatment for school-aged children on the autism spectrum (Wood et al. J Consult Clin Psychol 89:110–125, 2021). Twenty-nine of the 68 families of participants from a CBT intervention for autistic youth (Wood et al. J Consult Clin Psychol 89:110–125, 2021) who recorded home-based videos at pre-treatment also did so at post-treatment. Two measures were used by IEs to rate pre- and post-treatment home video recordings on children’s social isolation (Children’s Household-Environment Engagement Rating Scale; CHEERS, (Wood et al. Br J Clin Psychol, 2024) and Social Interaction Rating Scale (SIRS; Ruble et al. Topics Early Childhood Special Educ). Children in the CBT condition had a statistically significantly greater decline in CHEERS Solitary scores than did children in the Enhanced Standard Community Treatment (ESCT) condition. An increase in SIRS Responsive Parenting scores from pre- to post-treatment was statistically significantly linked with a decrease in Solitary scores. This study suggests that CBT-based interventions may be able to facilitate a positive impact on children’s social engagement in their home environment. This study provides an informative lens for considering the contextual validity of interventions for autistic children with IE-rated measures.