Background: Critically ill patients who are mechanically ventilated are at a high risk for malnutrition, which is associated with poor clinical outcomes. Aim: The aim of this study was to determine whether the modified version of Nutrition Risk in the Critically Ill (mNUTRIC) score predicts patients' clinical and functional outcomes in intensive care units (ICUs) in Jordan. Methods: A prospective, observational, quantitative research design was used. A convenience sample of 129 mechanically ventilated patients was recruited from ICUs in 7 hospitals across the different Jordanian health care sectors. Each patient was assessed and scored by the mNUTRIC tool.Results: Of the total 129 mechanically ventilated patients, the mean (SD) age of critically ill participants was 66.38 (17.46) years, 69.8% of the participants were male (n = 90), and 30.2% were female (n = 39). Approximately 88.4% of mechanical ventilator patients were at a high risk of malnutrition at the time of ICU admission. Overall, high mNUTRIC score (≥5) was significantly associated with MV duration ( P = .004), ICU length of stay ( P = .002), mortality (odds ratio, 5.43; P = .005), and functional outcomes (odds ratio, 0.184; P = .009).Relevance to Clinical Practice: Using nutrition risk screening tools such as the mNUTRIC score will add great benefits to nursing practice through identifying patients who are at a high risk of malnutrition within the first 48 hours of their admission in the ICU.