The Polyvagal Theory provides a new perspective to explore how autonomic nervous system function relates to social behavior, emotional regulation, and health. The Polyvagal Theory links the evolution of the autonomic nervous system to affective experience, emotional expression, facial gestures, vocal communication, and contingent social behavior. The theory, by being informed by the phylogeny of the autonomic nervous system, expands our understanding of normal and atypical behavior, mental health (e.g., coping with stress and novelty), experiences (e.g., dissociative states), and psychiatric disorders (e.g., autism, anxiety disorders, PTSD). The theory emphasizes that the core deficits in behavioral and affective regulation associated with several psychiatric disorders including autism are related to neural regulation of the autonomic nervous system. By incorporating a developmental perspective, the theory explains how atypical maturation and regulation of autonomic function forms the neural “platform” for the autism biobehavioral phenotype. The theory explains how the nervous system evaluates risk in the environment, without awareness and often independent of a cognitive narrative, through a process labeled “neuroception.” Neuroception attempts to support adaptive behaviors by matching autonomic state with the neuroceptive state of risk (i.e., safe social environment, danger, and life threat). According to the theory, autism is associated with a neuroception that protects the individual from others when there is no “real” danger resulting in defensive and often aggressive responses to friends and caregivers. The theory provides insights into strategies to reset neuroception to enable spontaneous social behavior, more optimally regulated autonomic state, and reduced auditory hypersensitivities.