Autism spectrum disorder (ASD) and attention-deficit/ hyperactivity disorder (ADHD) are common neurodevelopmental disorders (NDDs), categorized separately in the DSM-5 and International Statistical Classification of Diseases and Related Health Problems,. Yet, there are significant clinical and neurobiological similarities among children with either ASD or ADHD. Considerable clinical and neurobiological heterogeneity within disorders is also present. The etiology of either ASD or ADHD remains unclear, although perturbation in large-scale neural connectivity has been implicated across disorders based on the association of genes that regulate neural migration and synaptic development with both disorders 1 and case-control neuroimaging studies that demonstrated altered structural and functional connectivity across several neural networks in either disorder, compared with typically developing controls (TDCs). Although neuroscience research has provided important clues regarding neurodevelopmental alterations present in ASD and ADHD, findings that are inconsistent and nonspecific to either NDD limit the opportunities for clinical translation.