Background: Mortality rates of coronavirus disease-2019 (COVID-19) were too high across the globe. The impact of several risk factors on coronavirus mortality has been previously reported in several studies with different results. In this study, we aimed to investigate the relation between the patients' comorbidities and risk of mortality from critically ill COVID-19 disease. Methods: This is a prospective observational cohort study. Seventy-two patients with critically ill COVID-19 disease were included. All patients were adults (>18 years old) and diagnosed after SARS-CoV-2 PCR. All patients were admitted to isolation ICUs in critical care department, Cairo university hospitals. Results: Old age ( > 70 years-old) , DKA on presentation, receiving corticosteroids prior to presentation, thrombotic events (STEMI, N-STEMI, DVT) and tachypnea on admission were all risk factors for mortality with p-values 0.033, 0.031, 0.046, 0.013 and <0.001 respectively. Whereas, pre-existing pulmonary diseases did not have statistically significant relationship with mortality. Conclusion: Chronic comorbidities, complications, and demographic variables including old age, DKA, receiving corticosteroids prior to admission, thrombotic events and tachypnea are clinical risk factors for a fatal outcome associated with critically ill COVID-19 disease.