Background COVID-19 has emerged as a threat to human health. Liver dysfunction has been reported to occur frequently in patients with COVID-19, although its significance has not yet been elucidated. Methods The subjects were 35 patients with COVID-19, and clinical characteristics were retrospectively analyzed. COVID-19 patients requiring ventilator were classified as having severe COVID-19. Results All 35 patients were diagnosed as having mild-to-moderate COVID-19 at admission, but the severity aggravated to severe in 8 patients (22.9%) in hospital. Hepatocellular-type liver injury, defined as elevation of the serum AST and/or ALT levels to ≥ 3 times the ULN, was seen in 2 patients (5.7%), and cholestasis-type liver injury, defined as elevation of the serum ALP, γ-GTP and/or total bilirubin levels to ≥ twice the ULN, was seen in 4 patients (11.4%). A total of 9 patients (25.7%) fulfilled the criteria for liver injury. The percentage of patients with liver injury was higher in patients with severe COVID-19 than in the remaining patients ( P = 0.001). Both the hepatic CT attenuation values and the liver-to-spleen attenuation (L/S) ratios at admission were lower in the former patients than in the latter patients ( P < 0.001). ROC curve revealed the optimal cut-off value of the L/S ratio of 1.03 for discriminating between patients with severe and non-severe diseases. The hepatic CT attenuation values increased at the remission phase of the disease as compared to the values at admission ( P = 0.012). Conclusion Liver dysfunction associated with reduced hepatic CT attenuation values correlated with the disease severity in patients with COVID-19.