Introduction: the Global Leadership Initiative on Malnutrition (GLIM) was created to unify the diagnosis of malnutrition worldwide. The main objective of this work is to evaluate the validity of the GLIM criteria for diagnosing malnutrition in a population over 65 years of age living in a nursing home. In addition, the order of importance of the GLIM criteria for diagnosing malnutrition was also analyzed. Material and methods: a cross-sectional study was carried out with 130 older adults institutionalized in a nursing home. To study the validity of the GLIM criteria, sensitivity and specificity were calculated and a Receiver Operating Characteristic (ROC) curve was calculated using the MNA questionnaire as the reference diagnostic method. A Lasso regression model was used to determine the order of importance of the criteria. Results: according to GLIM and MNA the prevalence of malnutrition was 26.2 % and 18.5 %, respectively. The GLIM criteria were found to have a sensitivity of 100 %, a specificity of 91 % and a very good level of precision (AUC = 0.95). The order of importance of the criteria from highest to lowest are loss of muscle mass, weight loss, presence of inflammation, low BMI and decreased nutrient intake or assimilation. Conclusions: the GLIM criteria presented a satisfactory level of validity and are therefore an acceptable method to diagnose malnutrition in institutionalized older adults.