AIMS: Diabetes mellitus has been reported to be one of the most prevalent comorbidity in patients with Coronavirus Disease 2019 (COVID-19). We aimed to assess the association of comorbid diabetes with COVID-19 severity or mortality in China. METHODS: We performed a systematic literature search from six electronic databases on diabetes and COVID-19. The outcome of interest was disease severity or mortality. Heterogeneity among the studies was assessed by the Cochran Q test and the I(2) statistic. A random effects model was applied to calculate the pooled risk ratio (RR) with 95% confidence interval (CI). RESULTS: Nine studies from different provinces/cities were identified according to the predefined inclusion and exclusion criteria. There were a total of 1070 patients with diabetes, out of the 8807 COVID-19 cases. The majority of the cases were derived from Hubei Province. A low degree of heterogeneity in the risk estimates was observed in the included studies. Meta-analysis showed that there was a significant association of preexisting diabetes with disease severity or death. The pooled RR was 2.96 (95% CI: 2.31-3.79; p < 0.001). Sensitivity analysis demonstrated no significant changes in the pooled estimates. CONCLUSIONS: Comorbid diabetes was associated with an increased risk of disease severity or death in Chinese COVID-19 patients.