BACKGROUND: A pandemic of coronavirus disease (COVID-19) has been declared by the World Health Organization (WHO) and caring for critically ill patients is expected to be at the core of battling this disease. However, little is known regarding an early detection of patients at high risk of fatality. METHODS: This retrospective cohort study recruited consecutive adult patients admitted between February 8 and February 29, 2020, to the three intensive care units (ICUs) in a designated hospital for treating COVID-19 in Wuhan. The detailed clinical information and laboratory results for each patient were obtained. The primary outcome was in-hospital mortality. Potential predictors were analyzed for possible association with outcomes, and the predictive performance of indicators was assessed from the receiver operating characteristic (ROC) curve. RESULTS: A total of 121 critically ill patients were included in the study, and 28.9％ (35/121) of them died in the hospital. The non-survivors were older and more likely to develop acute organ dysfunction, and had higher Sequential Organ Failure Assessment (SOFA) and quick SOFA (qSOFA) scores. Among the laboratory variables on admission, we identified 12 useful biomarkers for the prediction of in-hospital mortality, as suggested by area under the curve (AUC) above 0.80. The AUCs for three markers neutrophil-to-lymphocyte ratio (NLR), thyroid hormones free triiodothyronine (FT3), and ferritin were 0.857, 0.863, and 0.827, respectively. The combination of two easily accessed variables NLR and ferritin had comparable AUC with SOFA score for the prediction of in-hospital mortality (0.901 vs. 0.955, P=0.085). CONCLUSIONS: Acute organ dysfunction combined with older age is associated with fatal outcomes in COVID-19 patients. Circulating biomarkers could be used as powerful predictors for the in-hospital mortality.