BACKGROUND: Since its first detection in December 2019, coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 infection has spread rapidly around the world. Although there have been several studies investigating prognostic factors for severe COVID-19, there have been no such studies in Korea. METHODS: We performed a retrospective observational study of 110 patients with confirmed COVID-19 hospitalized at a tertiary hospital in Daegu, Korea. Demographic, clinical, laboratory, and outcome data were collected and analyzed. Severe disease was defined as a composite outcome of acute respiratory distress syndrome, intensive care unit care, or death. RESULTS: Diabetes mellitus (odds ratio [OR], 19.15; 95% confidence interval [CI], 1.90-193.42; P = 0.012), body temperature >/= 37.8 degrees C (OR, 10.91; 95% CI, 1.35-88.36; P = 0.025), peripheral oxygen saturation < 92% (OR, 33.31; 95% CI, 2.45-452.22; P = 0.008), and creatine kinase-MB (CK-MB) > 6.3 (OR, 56.84; 95% CI, 2.64-1,223.78, P = 0.010) at admission were associated with higher risk of severe COVID-19. The likelihood of development of severe COVID-19 increased with an increasing number of prognostic factors. CONCLUSION: In conclusion, we found that diabetes mellitus, body temperature >/= 37.8 degrees C, peripheral oxygen saturation < 92%, and CK-MB > 6.3 are independent predictors of severe disease in hospitalized COVID-19 patients. Appropriate assessment of prognostic factors and close monitoring to provide the necessary interventions at the appropriate time in high-risk patients may reduce the case fatality rate of COVID-19.