Abnormal blood coagulation often occurs in critically ill patients, which seriously affects their prognosis. This retrospective study investigated the implications of changes in blood coagulation in patients with coronavirus disease 2019 (COVID-19). Records were reviewed for patients admitted with COVID-19 between February 4 and 16, 2020. The primary outcome was in-hospital death. A total of 85 patients were included, of whom 12 died in the hospital. The admission prothrombin time (PT), international normalized ratio (INR), and levels of D-dimer and fibrin/fibrinogen degradation products (FDP) were significantly higher in nonsurvivors than in survivors, while the reverse was true for prothrombin time activity (PT-act) and PaO 2 /FiO 2. Multivariate logistic regression showed that PT-act < 75% was independently associated with mortality. The area under the receiver operating characteristic curves for PT-act, D-dimer, and FDP at admission could significantly predict mortality. The AUCs for PT-act were larger than those for D-dimer and FDP; however, there was no significant difference. After 2 weeks of treatment, the coagulation parameters of the surviving patients improved. COVID-19 is often accompanied by abnormal coagulation. PT-act at admission is able to predict mortality in patients with COVID-19 as can D-dimer and FDP levels. PT-act < 75% is independently associated with mortality.