BACKGROUND: The aim of this study was to evaluate clinical outcomes in coronavirus disease 2019 (COVID-19) positive patients with type 2 diabetes compared to those without diabetes in Korea. METHODS: We extracted claims data for patients diagnosed with COVID-19 from the National Health Insurance Service database in Korea from January 20, 2020 to March 31, 2020. We followed up this cohort until death from COVID-19 or discharge from hospital. RESULTS: A total of 5,473 patients diagnosed with COVID-19 were analyzed, including 495 with type 2 diabetes and 4,978 without diabetes. Patients with type 2 diabetes were more likely to be treated in the intensive care unit (ICU) (P<0.0001). The incidence of inhospital mortality was higher in patients with type 2 diabetes (P<0.0001). After adjustment for age, sex, insurance status, and comorbidities, odds of ICU admission (adjusted odds ratio [OR], 1.59; 95% confidence interval [CI], 1.02 to 2.49; P=0.0416) and in-hospital mortality (adjusted OR, 1.90; 95% CI, 1.13 to 3.21; P=0.0161) among patients with COVID-19 infection were significantly higher in those with type 2 diabetes. However, there was no significant difference between patients with and without type 2 diabetes in ventilator, oxygen therapy, antibiotics, antiviral drugs, antipyretics, and the incidence of pneumonia after adjustment. CONCLUSION: COVID-19 positive patients with type 2 diabetes had poorer clinical outcomes with higher risk of ICU admission and in-hospital mortality than those without diabetes. Therefore, medical providers need to consider this more serious clinical course when planning and delivering care to type 2 diabetes patients with COVID-19 infection.