Purpose: This study aimed to compare long-term clinical outcomes according to the use of emergency medical services (EMS) in patients with ST-segment elevation myocardial infarction (STEMI) who arrived at the hospital within 12 hr of symptom onset. Materials and Methods: A total of 13104 patients with acute myocardial infarction were enrolled in the Korea Acute Myocardial Infarction Registry–National Institutes of Health from October 2011 to December 2015. Of them, 2416 patients with STEMI who arrived at the hospital within 12 hr were divided into two groups: 987 patients in the EMS group and 1429 in the non-EMS group. Propensity score matching (PSM) was performed to reduce bias from confounding variables. After PSM, 796 patients in the EMS group and 796 patients in the non-EMS group were analyzed. The clinical outcomes during 3 years of clinical follow-up were compared between the two groups according to the use of EMS. Results: The symptom-to-door time was significantly shorter in the EMS group than in the non-EMS group. The EMS group had more patients with high Killip class compared to the non-EMS group. The rates of all-cause death and major adverse cardiac events (MACE) were not significantly different between the two groups. After PSM, the rate of all-cause death and MACE were still not significantly different between the EMS and non-EMS groups. The predictors of mortality were high Killip class, renal dysfunction, old age, long door-to-balloon time, long symptom-to-door time, and heart failure. Conclusion EMS utilization was more frequent in high-risk patients. The use of EMS shortened the symptom-to-door time, but did not improve the prognosis in this cohort.