BACKGROUND: We evaluated the accuracy of the prehospital Field Triage Decision Scheme, which has recently been applied in the Korean trauma system, and the factors associated with severe injury and prognosis at a regional trauma center in Korea. METHODS: From 2016 to 2018, prehospital data of injured patients were obtained from the emergency medical services of the national fire agency and matched with trauma outcomes at our institution. Severe injury (Injury Severity Score > 15), overtriage/undertriage rate, positive predictive value, negative predictive value, and accuracy were reviewed according to the triage protocol steps. A multivariate logistic regression analysis was performed to identify influencing factors in the field triage. RESULTS: Of the 2438 patients reviewed, 853 (35.0%) were severely injured. The protocol accuracy was as follows: step 1, 72.3%; step 2, 65.0%; step 3, 66.2%; step 1 or 2, 70.2%; and step 1, 2, or 3, 66.4%. Odds ratios (OR) (95% confidence interval [CIfor systolic blood pressure < 90 mmHg (3.535 [1.920-6.509]; p < 0.001), altered mental status (17.924 [8.980-35.777]; p < 0.001), and pedestrian injuries (2.473 [1.339-4.570], p = 0.04) were significantly associated with 24-h mortality. Penetrating torso injuries (7.108 [4.108-12.300]; p < 0.001); two or more proximal long bone fractures (4.134 [2.316-7.377]); p < 0.001); crushed, degloved, and mangled extremities (8.477 [4.068-17.663]; p < 0.001); amputation proximal to the wrist or ankle (42.964 [5.764-320.278]; p < 0.001); and fall from height (2.141 [1.497-3.062]; p < 0.001) were associated with 24-h surgical intervention. CONCLUSION: The Korean field triage protocol is not yet accurate, with only some factors reflecting injury severity, making reevaluation necessary.