Triage is essential for rapid and efficient intervention in patients visiting an emergency department. In Korea, since 2016, the Pediatric Korean Triage and Acuity Scale (PedKTAS) has been implemented nationwide for the triage of patients visiting pediatric emergency departments (PEDs). The aim of this study was to evaluate the validity of the PedKTAS in patients who visit PEDs. This study was a retrospective observational study of national registry data collected from all emergency medical centers and institutions throughout Korea. We analyzed data from patients aged <15 years who visited emergency departments nationwide from January 2016 to December 2019. The hospitalization and intensive care unit (ICU) admission rates were analyzed on the basis of triage level. In total, 5,462,964 pediatric patients were included in the analysis. The hospitalization rates for PedKTAS Levels 1–5, were 63.5%, 41.1%, 17.0%, 6.5%, and 3.7%, respectively, and were significantly different (p< 0.001). The ICU admission rates for PedKTAS Levels 1–5 were 14.4%, 6.0%, 0.3%, 0.1%, and 0.1%, respectively, and were significantly different (p< 0.001). The hospitalization and ICU admission rates were highest for PedKTAS Level 1, and differences were significant based on the level. We identified that the PedKTAS is suitable for predicting the emergency status of pediatric patients who visit PEDs.