Aims To assess the effect of cognitive function, performance of activities of daily living (ADLs), degree of depression, and fear of infection among geriatric patients hospitalized in internal medicine wards for COVID-19 on the duration of hospitalization and in-hospital mortality. Methods This observational survey study was conducted during the second, third, and fourth waves of the COVID-19 pandemic. The study included elderly patients of both sexes, aged ≥ 65 years, hospitalized for COVID-19 in internal medicine wards. The following survey tools were used: AMTS, FCV-19S, Lawton IADL, Katz ADL, and GDS15. The duration of hospitalization and in-hospital mortality were also assessed. Results A total of 219 patients were included in the study. The results showed that impaired cognitive function in geriatric patients (AMTS) was associated with higher in-hospital mortality among COVID-19 patients. There was no statistical significance between fear of infection (FCV-19S) and risk of death. The impaired ability to perform complex ADLs (Lawton IADL) before the onset of the disease was not associated with higher in-hospital mortality among COVID-19 patients. The diminished ability to perform basic ADLs (Katz ADL) before the onset of the disease was not associated with higher in-hospital mortality in COVID-19. The degree of depression (GDS15) was not associated with higher in-hospital mortality in COVID-19 patients. Statistically, significantly better survival was observed for patients with normal cognitive function (p = 0.005). No statistically significant differences in survival were observed in relation to the degree of depression or independence in performing ADLs. Cox proportional hazards regression analysis showed a statistically significant effect of age on mortality (p = 0.004, HR 1.07). Conclusion In this study, we observe that cognitive function impairments and the older age of patients treated for COVID-19 in the medical ward increase the in-hospital risk of death.