The study aimed to analyze the demographic, comorbidities, biomarkers, pharmacotherapy, and ICU-stay with the mortality outcome of COVID-19 patients admitted in the intensive care unit of a tertiary care hospital in a low-middle income country, Bangladesh. Methods: The retrospective cohort study was done in Holy Family Red Crescent Medical College Hospital from May to September 2020. All 112 patients who were admitted to ICU as COVID-19 cases (confirmed by RT-PCR of the nasopharyngeal swab) were included in the study. Demographic data, laboratory reports of predictive biomarkers, treatment schedule, and duration of ICU-stay of 99 patients were available and obtained from hospital records (non-electronic) and treatment sheets, and compared between the survived and deceased patients. Results: Out of 99 patients admitted in ICU with COVID-19, 72 were male and 27 were female. The mean age was 61.08 years. Most of the ICU patients were in the 60 - 69 years of age group and the highest mortality rates (35.89%) were observed in this age range. Diabetes mellitus and hypertension were the predominant comorbidities in the deceased group of patients. A significant difference was observed in neutrophil count, creatinine and, NLR, d-NLR levels that raised in deceased patients. There was no significant difference as a survival outcome of antiviral drugs remdesivir or favipiravir, while the use of cephalosporin was found much higher in the survived group than the deceased group (46.66% vs 20.51%) in ICU. Conclusions: Susceptibility to developing critical illness due to COVID-19 was found more in comorbid males aged more than 60 years. There were wide variations of the biomarkers in critical COVID-19 patients in a different population, which put the healthcare workers into far more challenge to minimize the mortality in ICU in Bangladesh and around the globe during the peak of the pandemic.