The COVID-19 pandemic, starting in 2020, changed the daily activities of people in the world and it might also affect patterns of major trauma. This study aimed to compare the epidemiology and outcomes of trauma patients before and after the COVID-19 outbreak. This was a retrospective study, conducted in a single regional trauma center in Korea, and patients were grouped as pre- and post-COVID-19 and compared in terms of demographics, clinical characteristics, and clinical outcomes. A total of 4585 patients were included in the study and the mean age was 57.60 ± 18.55 and 59.06 ± 18.73 years in the pre- and post-COVID-19 groups, respectively. The rate of elderly patients (age ≥ 65) significantly increased in the post-COVID-19 group. In terms of injury patterns, self-harm was significantly increased after COVID-19 (2.6% vs. 3.5%, p = 0.021). Mortality, hospital length of stay, 24 h, and transfusion volume were not significantly different. Among the major complications, acute kidney injury, surgical wound infection, pneumonia, and sepsis were significantly different between the groups. This study revealed changes in the age of patients, injury patterns and severity, and major complication rates after the COVID-19 outbreak.