Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by impaired functioning in two domains: (1) social communication and interaction, and (2) restricted interests, repetitive behaviors, and sensory sensitivities. The present study examined affect-related postauricular responses to social and nonsocial pictures in children with ASD using a protocol that integrated psychophysiology, caregiver ratings of symptom severity, and Ecological Momentary Assessments (EMA). Results were suggestive of greater postauricular responses among children with ASD while viewing nonsocial images related to circumscribed interests but not other nonsocial images or social images, indicative of greater positive affective responses to images related to circumscribed interests compared to their typically developing peers. Correlations between psychophysiological responses and symptom severity in both core autism domains (i.e., social deficits and restricted interests) were examined, as were correlations with self-reported affect obtained via EMA. The results of this study suggest that postauricular reflex responses may be a useful tool for studying affective responses in children with ASD.