Assessing nutritional status is vital for understanding and managing patients' clinical conditions. Controlling Nutritional Status (CONUT) score is one of the most frequently used scores that evaluate caloric status, protein reserve, and immunological response estimation. This study assesses the critically ill patients' nutritional status and its relationship with patient-related factors and mortality. Electronic medical records of 1687 Intensive Care Unit (ICU) patient files were reviewed from January 2019 to May 2023 retrospectively. Patient demographic information, clinical characteristics, and laboratory data were extracted and anonymized for analysis. The patients were divided according to the CONUT scores, and retrieved data were compared. The study population's demographic features and clinical outcomes were stratified by CONUT scores. The gender distribution was similar; however, there was a significant age difference between the Low-CONUT and High-CONUT groups (P < .001). High CONUT values are linked to an increased risk of death, intubation, age, APACHE-II scores, and the number of comorbidities. Malnutrition is prevalent in ICU patients with gastrointestinal illnesses and urogenital system disorders, including infections. Patients with a high CONUT score at admission had an increased risk of ICU death even after correcting for covariates. The CONUT score is a trustworthy and practical tool for assessing ICU patients' nutritional status, which is highly associated with ICU mortality. Patients admitted to the ICU with gastrointestinal, urogenital, or infectious disorders should have their nutritional condition assessed carefully. According to our study, the rate of intubated patients admitted to the intensive care unit is higher in malnourished patients. This suggests it should be reviewed in clinical settings, particularly in elderly, frail patients and those with numerous comorbidities.