According to cognitive models of social anxiety disorder (SAD), both anticipatory processing and post-event processing are core mechanisms in disorder maintenance leading to dysfunctional coping with social situations through negative self-evaluation and increased anxiety. To date, little is known about these processes during late childhood, a critical period for disorder development. Further, it remains unclear if dysfunctional rumination in children can be altered through psychotherapeutic interventions such as cognitive distraction. In the current study, children aged 9 to 13 years with SAD and age- and gender-matched healthy controls (HCs, each: n = 30) participated in an experimental laboratory social stress task while anticipatory processing, post-event processing, subjective anxiety, self-evaluations, and autonomic arousal (skin conductance level) were assessed. Further, the impact of a brief cognitive distraction intervention on post-event processing was assessed. Children with SAD reported more negative anticipatory and post-event processing compared to HC children. Further, negative anticipatory processing was associated with higher subjective anxiety and reduced subjective performance ratings during the social stress task. In the aftermath of the stressor, distraction led to reduced subjective anxiety in the group with SAD and lower autonomic arousal in all children but did not alter post-event processing. The current study suggests that both anticipatory and post-event processing already play a key role in the maintenance of SAD in childhood. While distraction may be beneficial in reducing prolonged subjective anxiety and autonomic arousal after social situations, more research on interventions targeting ruminative processes is needed.