ObjectivesBicycles and motorcycles are the main means of transportation and leisure for those under the age of 19 in South Korea. We aimed to identify epidemiology of injuries and to determine the injury characteristics and clinical outcomes of two-wheel vehicle-related accidents in individuals under the age of 19.Materials and methodsThis was a retrospective cohort and data, acquired from the National Emergency Department Information System, was collected from 401 emergency departments (EDs) between January 2016 and December 2018. We included injured patients aged < 19 years who experienced injuries while driving two-wheeled vehicles.Results We enrolled 54,342 two-wheel vehicle injury patients in the study (37,410 bicycle and 16,932 motorcycle-related), of which, males comprised 86.8% (bicycle) and 94.9% (motorcycle). External and extremity injuries were the most common injuries. ED mortality was 9 (0.0%) for bicycle injury and 53 (0.3%) in motorcycle injury. 3,346 (8.9%) patients with bicycle injuries and 4,096 (24.2%) with motorcycle injuries were hospitalised. Bicycle-related injuries included fractures in the clavicle (10.9%), humerus (13.4%), and forearm (25.4%). Motorcycle-related injuries included fractures in the pelvic ring (2.0%), acetabular (0.9%), femoral (10.2%), patellar (1.8%), tibiofibular (11.5%) and foot (7.5%). The mean ISS score of hospitalised patients was 12.0 ± 12.6 in bicycle-related injury and 17.6 ± 15.4 in motorcycle-related injury. The number of hospitalised bicycle injury patients with ISS > 16 of was 922 (27.6%), and that of hospitalised motorcycle injury patients with ISS > 16 was 1,850 (45.2%). The mean length of hospital stay (LOS) was 191.5.8 ± 224.2 hours in bicycle injury, while the mean LOS for motorcycle injury was 359.6 ± 416.7 hours. Hospital mortality cases were 6 (0.2%) with bicycle injury and 49 (1.2%) with motorcycle injury. Conclusions In the under-19 population, two-wheel vehicle-related injuries had a low mortality rate and occurred predominantly in males. Motorcycle injuries were higher in patients aged over 16 and were associated with higher ISS (>16), ICU admissions, and mortality rates than bicycle injuries. Bicycle accidents mainly caused upper limb fractures, while motorcycle accidents mainly caused lower limb fractures. Preventive measures according to each means and age group are required.