Although bivariate associations between attention-deficit/hyperactivity disorder (ADHD) and eating disorders in adolescent girls and boys have been previously identified, the mechanistic link underlying the symptom-level associations remains unclear. We evaluated shared genetic and environmental influences on ADHD symptoms and disordered eating in 819 female and 756 male twins from the Swedish TCHAD cohort using bivariate models. Common additive genetic and unique environmental effects accounted for majority of ADHD and disordered eating associations in a differential manner. For girls, the strongest genetic correlation was observed for cognitive/inattention problems-bulimia (0.54), with genetic factors accounting for 67% of the phenotypic correlation. For boys, the strongest genetic correlations were observed for conduct problems-bulimia and hyperactivity-bulimia (~ 0.54), accounting for 83% and 95% of the phenotypic correlation, respectively. As per our findings, the risk of comorbidity and shared genetics highlights the need for preventative measures and specialized treatment for ADHD and disordered eating in both sexes.