Purpose: Emergency department (ED) is a common treatment setting for adolescents with clinically serious self-harm. Here, we investigated the clinical characteristics and trends of adolescents with self-harm who visited the ED in one Korean university hospital. We also compared patients with a single ED visit to those with multiple ED visits to identify the risk factor of repeated visits. Materials and Methods: We retrospectively identified patients aged 12 to 18 years who presented to ED for self-harm from January 2015 to December 2019, based on electronic medical records. Self-harm included all thoughts and behaviors indicating intents to harm or hurt oneself, regardless of the degree of such attempt. Results: A total of 168 individuals (male:female=31:137; average 15.99±1.64 years) presented to ED following 304 episodes (45 and 259 episodes in males and females, respectively). The number of episodes steeply increased between 2016 and 2019, and the overall number during the study showed an increasing trend (p=0.043). Repeated ED visitors with self-harm showed more history of psychiatric treatment/admission (58.3% vs. 85.4%, p=0.002; 14.2% vs. 43.9%, p<0.001), history of child abuse (32.3% vs. 53.7%, p=0.013), and familial psychiatric history (13.4% vs. 31.7%, p=0.008) compared to those with a single visit. Conclusion Among Korean adolescents, the number of ED visits and repetition of ED visits for self-harm is on the rise. For adolescents presenting to ED with self-harm, the history of psychiatric treatment/admission, child abuse, and familial psychiatric history should be properly obtained to identify the risk for multiple ED visits.