Autistic children tend to show divergent social information processing, and controversies exist regarding the mechanisms underlying this processing. In this article, we summarize and categorize the current theories and evidence related to hypo- and hyperarousal accounts of social information processing in autism. The hypo-arousal account proposes reduced motivation or sensitivity to process social information and is supported by behavioral, eye-tracking, and neuroimaging studies. Recent evidence has challenged this account, highlighting the role of eye gaze in interpreting the hypo-brain activation. The hyperarousal account posits that social context could evoke anxiety and discomfort in autistic children, which could interfere with their social information processing and result in social avoidance. Most research in this field has studied children and adolescents, but some studies have included adults since autism is a lifelong condition. Here, we highlight the importance of considering the heterogeneity of arousal patterns in autistic children when developing individualized supporting protocols.