Background Concomitance with diabetes is associated with high mortality in critical conditions. Patients with previous diabetes are more vulnerable to COVID-19. However, new-onset COVID-19-related diabetes (CRD) and its relevance have scarcely been reported. This study investigates new-onset CRD and its correlation with poor outcomes or death in patients with COVID-19. Methods We performed a single center, retrospective case series study in 120 patients with laboratory confirmed COVID-19 at a university hospital. Fasting blood glucose (FBG) ≥7.0 mmol/L for two times during hospitalization and without a history of diabetes were defined as CRD. The Critical status was defined as admitted to intensive care unit (ICU) or death. Results After excluding patients with a history of diabetes, chronic heart, kidney, and liver disease, 69 patients with COVID-19 were included in the final analysis. Of the 69 patients, 23 were Moderate, 20 were Severe, and 26 were Critical (including 16 deceased patients). The prevalence of CRD in Critical and Moderate+Severe patients was 53.85% and 13.95%, respectively. Kaplan-Meier survival analysis revealed a significantly higher mortality rate in patients with CRD (P=0.0019). Multivariable analysis indicated that CRD was an independent predictor for death (HR = 3.75, 95% CI 1.26-11.15). Cluster analysis suggested that indicators for multi-organ injury were interdependent, and more proximities of FBG with indicators for multi-organ injury was present. Conclusion Our results suggest that new onset COVID-19-related diabetes is an indicator of multi-organ injury and predictor for poor outcomes and death in COVID-19 patients. As it is easy to perform for clinical practices and even self-monitoring, glucose testing will be much helpful for predicting poor outcomes to facilitate appropriate intensive care in patients with COVID-19.