Associations between variability in sympathetic nervous system arousal and individual differences in symptom severity were examined for children with autism spectrum disorder (ASD). Thirty-four families participated in a laboratory visit that included continuous measurement of electrodermal activity (EDA) during a battery of naturalistic and structured parent–child, child alone, and direct testing tasks. Multiple indices of EDA were considered. Greater variability in EDA was associated with higher levels of ASD symptoms, with findings generally consistent across tasks. Intellectual functioning did not moderate the relation between EDA and ASD symptoms. Sympathetic arousal tendencies may represent an important individual difference factor for this population. Future directions and conceptualizations of EDA are discussed.