Objective: This study analyzed patients who visited emergency departments (EDs) following suicide and self-harm attempts to determine the impact of the coronavirus disease 2019 (COVID-19) on suicide and self-harm trends. Methods: This study retrospectively collected the data of patients who visited five EDs following suicide and self-harm attempts before (March to December 2019) and after (March to December 2020) the COVID-19 outbreak using the National Emergency Department Information System database in South Korea. Results: In this study, 2,333 and 2,303 patients visited EDs following suicide and self-harm attempts before and after COVID-19, respectively. The number of females was 1,421 versus 1,490 (P=0.008), and the number of those in their twenties (20s) was 576 versus 705 (P<0.001), respectively. The proportion of patients with suicide attempts increased after the outbreak (1.0 vs. 0.7%; P=0.009). The severity scores on the Korean Triage and Acuity Scale (KTAS) levels 1 and 2 decreased-before 169 (7.2%) and 633 (27.1%); after 144 (6.3%) and 525 (22.8%); P=0.003. The outcomes of patients following hospital admission were significantly different in terms of increased safe discharge numbers, decreased discharges against medical advice and transfers to other hospitals, and fewer deaths during admission. Conclusion During the COVID-19 outbreak, there were notable characteristic changes in the rate of suicide attempts in young adults, with the decreased severity of suicide and self-harm among the patients who visited EDs.