Objective: Previous studies have linked ADHD with self-harm, but the processes underlying this association are not fully understood. This research aims to investigate the role of sleep disturbances as a potential pathway between ADHD diagnosis and self-harm behaviors. Materials and Methods: The study included 90 youth aged between 11 and 18 years, divided into two groups: a case group of 45 youth diagnosed with ADHD and a control group of 45 youth without ADHD. Both groups completed the Inventory of Statements About Self-Injury to evaluate self-harm behaviors and the Sleep Disturbance Scale for Children to assess sleep disturbances. A path analysis was conducted to examine whether a significant proportion of the association between ADHD and self-harm was shared with sleep disturbances, while controlling for gender, youth education, family income, maternal education, and overall anxiety and depression scores. Results: An ADHD diagnosis was significantly associated with sleep disturbances ([beta] = 0.62, p < 0.001) and self-harm behaviors ([beta] = 0.35, p = 0.03). Additionally, sleep disturbances were significantly linked to self-harm ([beta] = 0.51, p = 0.002) and played a significant role in the association between ADHD and self-harm (indirect effect [beta] = 0.32, p = 0.001). Conclusion: These findings suggest that sleep disturbances account for a substantial proportion of the shared variance in the association between ADHD and self-harm. While the cross-sectional design limits causal interpretations, these results highlight the importance of addressing sleep issues in clinical care for ADHD to potentially reduce self-harm risks and improve outcomes for at-risk youth.