Background In critical care patients, the nutritional status is related to many factors such as existing co-morbidities, nutritional history, and the current disease. It is crucial to apply a comprehensive nutritional assesment and to start nutritional support as soon as possible in intensive care unit(ICU) where malnutrition is common. There are many studies on association between modified Nutritional Risk in Critical Patients (mNUTRIC) score and outcome in ICU patients but the effectiveness of tools for risk assesment isn’t still remains unclear. We aimed to define the correlation between the mNUTRIC score and 28-day mortality in patients with chronic obstructive pulmonary disease (COPD) in ICU. Materials and Methods The admission of COPD patients to the respiratory ICU in 2018 were determined retrospectively. Demograpic data of all patients, body mass index (BMI), mNUTRIC scores, Acute Physiology and Chronic Health Assessment II (APACHE II), Sequential Organ Failure Assessment (SOFA) scores, Charlson Comorbidity Index (CCI), time from patient ward to ICU admission, sepsis parameters including C-reactive protein (CRP) and procalcitonin, ICU length of stay (LOS ICU), vasopressor use, and 28-day mortality were recorded. Results 159 COPD patients involved the study. Age, CCI, day from patient ward to ICU admission, SOFA score, APACHE II score and 28-day mortality were detected to be statistically higher in patients with mNUTRIC ≥ 5 (p < 0.05). Conclusion The mNUTRIC score could be an proper method for nutritional risk to predict prognosis in critically ill COPD patients.