For a study, youth with autism spectrum disorder (ASD), increased stress response and/or atypical autonomic nervous system (ANS) regulation to benign social encounters may therefore influence social behaviors, and, along with developmental and experiential factors, shape psychological outcomes. For a study, the researchers measured ANS response to a peer-based social interaction paradigm in 50 typically developing (TD) children and 50 children with ASD (ages 10–13). Linear mixed models revealed that, while there were no diagnostic effects for respiratory sinus arrhythmia (RSA) or pre-ejection period (PEP), older youth with ASD appeared to demonstrate a blunted parasympathetic (RSA) response. Further, increased severity of parent-reported social symptoms was related to lower RSA. Youth with ASD reported more anxiety following the interaction. However, symptoms were not related to RSA or PEP response based on linear mixed modeling. Physiological regulation, age, and social functioning likely influence stress responses to peer interactions for youth with ASD. Parasympathetic functioning, as opposed to sympathetic arousal, may be especially important in behavioral regulation, as older youth with ASD demonstrated atypical regulation and response to the social interaction paradigm. Future research should help to further elucidate the developmental factors contributing to stress responses in ASD, the effect of physiological response on observable social behavior, and potential long-term consequences of chronic social stress in youth with ASD.