The Trier Social Stress Test (TSST) was employed to study response to social evaluative threat in male adolescents with Autism Spectrum Disorder (ASD, n = 21) and typical development (n = 13). Participants wore a mobile electrocardiogram to collect heart rate data. There were significant group effects on respiratory sinus arrhythmia (RSA), a measure of parasympathetic nervous system function, with lower values in ASD (F = 4.97). Bivariate correlations also showed a significant relationship between parent reports of social problems and RSA response to the TSST (r = -0.586). These findings suggest that autonomic dysregulation may contribute to social deficits in adolescents with ASD.