Background: The kidney represents a potential target for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Acute kidney injury (AKI) can occur through several mechanisms and includes intrinsic tissue injury by direct viral invasion. Clinical data about the clinical course of AKI are lacking. We aimed to investigate the proportion, risk factors, and prognosis of AKI in critical patients affected with coronavirus disease 2019 (COVID-19).Methods: A case/control study conducted in two intensive care units of a tertiary teaching hospital from September to December 2020.Results: Among 109 patients, 75 were male (69%), and the median age was 64 years (interquartile range [IQR], 57–71 years); 48 (44%) developed AKI within 4 days (IQR, 1–9). Of these 48 patients, 11 (23%), 9 (19%), and 28 (58%) were classified as stage 1, 2, and 3, respectively. Eight patients received renal replacement therapy. AKI patients were older and had more frequent sepsis, acute respiratory distress syndrome, and rhabdomyolysis; higher initial urea and creatinine; more marked inflammatory syndrome and hematological disorders; and required more frequent mechanical ventilation and vasopressors. An elevated level of D-dimers (odds ratio [OR], 12.83; 95% confidence interval [CI], 1.9–85) was an independent factor of AKI. Sepsis was near to significance (OR, 5.22; 95% CI, 0.94–28; P=0.058). Renal recovery was identified in three patients. AKI, hypoxemia with the ratio of the arterial partial pressure of oxygen and the inspiratory concentration of oxygen <70, and vasopressors were identified as mortality factors.Conclusions: AKI occurred in almost half the patients with critical COVID-19. A high level of D-dimers and sepsis contributed significantly to its development. AKI significantly worsened the prognosis in these patients.