Background: Since the beginning of the coronavirus disease of 2019 (COVID-19) pandemic, concerns raised by the growing number of deaths worldwide. Acute respiratory distress syndrome (ARDS) and extrapulmonary complications can correlate with prognosis in COVID-19 patients. This study evaluated the association of systemic complications with mortality in severely affected COVID-19 patients. Materials and Methods: This retrospective study was done on 51 intensive care unit (ICU)-admitted COVID-19 adult patients who were admitted to the ICU ward of Khorshid hospital, affiliated with Isfahan University of Medical Sciences. Only the patients who had a definite hospitalization outcome (dead vs. survivors) were included in the study. Daily clinical and paraclinical records were used to diagnose in-hospital complications in these patients. Results: The sample was comprised of 37 males (72.5%) and 14 females (27.4%). The median age of patients was 63 years (Min: 20, Max: 84), with the mortality rate of 47.1%. In total, 70.6% of patients had at least one coexisting disorder. Chronic kidney disease was associated with the worse outcome (29.16% of dead patients against 3.70 of survived ones). Mechanical ventilation was used in 58.8% of patients. Patients who had received invasive ventilation were more likely to die (87.50% of dead patients against 7.40 of survivors), Complications including sepsis and secondary infections (odds ratio: 8.05, confidence interval: 2.11–30.63) was the strongest predictors of mortality. Conclusion: Complications including sepsis and secondary infections can increase the risk of death in ICU-admitted COVID-19 patients. Therefore, it is substantial that the physicians consider preventing or controlling these complications.