Although the comorbidity of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) (ASD+ADHD) is prevalent, the neurobiological mechanisms underlying this combined condition are not yet fully understood. Both ASD and ADHD have been associated with alterations in gray matter (GM) structural networks, suggesting that such altered GM networks may serve as potential markers for identifying this comorbid disorder. In this study, we compared the GM structural networks in ASD+ADHD, ASD without ADHD (ASD-only), ADHD without ASD (ADHD-only), and typically developing controls (TDc). Structural magnetic resonance imaging data of 41 individuals with ASD+ADHD, 53 individuals with ASD-only, 40 individuals with ADHD-only, and 62 TDc were obtained from the Autism Brain Imaging Data Exchange II and the ADHD-200 Sample databases. Graph theory analysis was employed to construct individual GM structural networks for each participant, followed by the calculation of topological metrics based on these networks. Our analysis revealed both common and disorder-specific nodal centralities alterations across the ASD+ADHD, ASD-only, and ADHD-only groups, compared with TDc. A significant correlation was found between the severity of symptoms and altered nodal centralities in the amygdala in the ASD+ADHD group. These findings support the Diagnostic and Statistical Manual of Mental Disorders-5 diagnosis of ASD+ADHD. Moreover, these findings provide novel neurobiological evidence for the ASD+ADHD comorbid state, which could lead to more targeted diagnostic and therapeutic approaches.