We explored the role of negative performance beliefs and self-focused attention considered central to psychological models of social anxiety but not studied in autism. Firstly, we compared self- and observer ratings of performance on a social task for 71 young autistic people, 41 high and 30 low in social anxiety, finding a significant main effect of social anxiety but not rater. Subsequently, 76 autistic young people, 46 high and 30 low social anxiety completed measures of interoceptive sensibility and focus of attention following a social task. Only heightened interoceptive sensibility fully mediated the relationship between self-ratings of social performance and social anxiety. These findings suggest awareness of bodily sensations are critical to anxiety in social situations with implications for treatment.