Coronavirus disease 2019 (COVID-19) quickly reached the pandemic status, with 765.22 million confirmed cases of COVID-19 and 6.92 million COVID-19 deaths reported worldwide by May 2023. Due to its sudden and global nature, the COVID-19 pandemic has had a significant impact on the emotional and mental health of many people. A group of COVID-19 patients who frequently require intensive care are geriatric patients. The cognitive performance of these patients and their independence in instrumental activities of daily living (IADL) may be crucial to their prognosis and risk of in-hospital death. The present study aimed to assess the level of independence in activities of daily living (ADL), mental fitness, the level of fear of COVID-19, and cognitive functions to determine their impact on in-hospital mortality in geriatric COVID-19 patients. A total of 300 intensive care unit (ICU) patients with COVID-19 were included in the cross-sectional study, using the following questionnaires: the Lawton IADL scale, the Katz ADL index of independence, the fear of COVID-19 scale (FCV-19S), the abbreviated mental test score (AMTS), and the 15-item geriatric depression scale (GDS15). Patients aged 64 or below reported significantly greater independence on the IADL scale and the basic ADL scale, and showed a significantly higher level of mental fitness (Mann-Whitney U test; p = 0.001). Patient survival and in-hospital mortality were influenced by independence in basic and complex ADL. The level of independence is an important prognostic indicator for in-hospital mortality in geriatric COVID-19 patients. The higher the level of mental fitness, the higher the level of independence in basic and instrumental activities of daily living. Patients aged ≥65 years are less independent in basic and instrumental activities of daily living. Moreover, they show a significantly lower level of cognitive functions.