Background: There are insufficient studies on clinical and environmental factors that affect the use of emergency medical services (EMS) in pediatric patients. Objectives: We sought to identify the clinical characteristics of pediatric patients transported to the emergency department (ED) by EMS and meteorological factors affecting the use of EMS. Methods: We reviewed the medical records of patients younger than 19 years who visited the ED from January 2005 to December 2019. Results: The rate of EMS use was higher among older patients [adjusted odds ratio (aOR): 1.12; 95% confidence interval (CI): 1.11 -1.13] and increased with disease severity (aOR: 0.35; 95% CI: 0.33 -0.37 for KTAS and aOR: 0.73; 95% CI: 0.70 -0.77 for GCS). The rate of EMS use was higher in patients with injury than in those with disease (aOR:3.47; 95% CI: 3.15 -3.83). Compared with winter, the summer season was a risk factor for EMS use (aOR: 1.36; 95% CI: 1.08-1.72). Precipitation greater than 40 mm per day increased the risk of EMS use (aOR: 1.31; 95% CI: 1.03-1.72), as did higher concentrations of O(3 )and NO2 (aOR per 0.001 ppm: 1.006; 95% CI: 1.001-1.011 for O-3 and aOR per 0.001 ppm: 1.02; 95% CI: 1.01-1.03 for NO2, respectively). Conclusions: Several clinical characteristics, meteorological factors, and air pollutants might increase the risk of EMS use among pediatric patients.