<p>Attention-Deficit/Hyperactivity Disorder (ADHD) is a prevalent public health issue in childhood and adolescence, often associated with self-harm (defined here as non-suicidal self-injury; NSSI) and suicidality. However, the nature of this relationship warrants further investigation, as it can be influenced by various factors within the ecological systems perspective, further intensifying these risks. This study aimed to investigate the direct association between ADHD symptoms, self-harm, and suicidality, and conducted propensity score matching (PSM) to isolate the unique effects of ADHD on self-harm and suicidality. Data were drawn from 6,689 Korean adolescents collected by the Korean National Youth Policy Institute in 2021. The results indicated a significant association with higher levels of self-harm (AOR = 1.25, p &lt; .05), while no significant association was observed with suicidality (AOR = 0.79, p &gt; .05) after PSM. Notably, distinct self-harm behaviors exhibited varied patterns; for example, self-inflicted stabbing with a knife was significantly lower (AOR = 0.73, p &lt; .01), while self-inflicted head banging was significantly higher (AOR = 1.29, p &lt; .01) among those in the ADHD-risk group. These findings suggest that ADHD traits may contribute to immediate stress-induced self-harm rather than suicidal intent, with comorbid conditions playing a pivotal role in suicidal behavior. Intervention implications should incorporate a holistic, ecological perspective that considers the role of contextual factors rather than focusing solely on symptomatology. To effectively reduce ADHD-related risks, targeted interventions that foster resilience and mitigate impulsive self-harm are essential for social workers.</p>