Autism spectrum disorder (ASD) and schizophrenia spectrum disorders (SZS) are both characterized by atypical social behavior and cognition. Common genetic pathways and neural processes are implicated in both disorders, but few studies have directly compared clinical populations with ASD and SZS. For this reasons, shared and distinct characteristics are poorly understood. This panel presents four studies applying complementary methods at multiple levels of analysis, spanning brain structure to neurophysiology to psychophysiological assessment of behavior to clinical observation and self-report. These novel approaches are applied to converge upon functional processes related to core features of both disorders: social-communication, gaze perception, neural connectivity, and sensory processing. At the level of clinical symptomatology, results concord with behaviorally defined diagnostic categories. In contrast, measures of specific neural mechanisms and functional processes indicate significant overlap in ASD and SZS, aligning with performance at both clinical and subclinical levels rather than diagnostic taxon. Discovery of shared neural bases of phenomenologically distinct disorders holds promise for understanding specific strengths and vulnerabilities and offers straightforward clinical implications. Panel discussion focuses on relevance to a dimensional characterization of neurodevelopmental disorders and its implications for biomarker development in ASD.