Understanding age-specific injury patterns allows the continued improvement of prevention strategies. This is a retrospective study analyzing the Korea Emergency Department-Based Injury In-depth Surveillance data, including those aged ≤19 years old between January 2011 and December 2017. In this study, we focused on changes in the modes of injury and severity, and prevention potential by dividing the patients into four age groups: group 1 (0–4 years), group 2 (5–9 years), group 3 (10–14 years), and group 4 (15–19 years). The most common mode of injury in younger age groups 1 and 2 was a fall or slip. Most injuries in older age groups 3 and 4 were unintentional and intentional collisions combined. Traumatic brain injuries (2.1%), intensive care unit admissions (1.8%), and overall death (0.4%) were the highest in group 4. The proportions of severe and critical injury (EMR-ISS ≥ 25) were 7.5% in group 4, 3.2% in group 3, 2.5% in group 1, and 1% in group 2. This study presents a comprehensive trend of injuries in the pediatric population in South Korea. Our results suggest the importance of designing specific injury-prevention strategies for targeted groups, circumstances, and situations.