The two-step Global Leadership Initiative on Malnutrition (GLIM) approach was recently introduced to malnutrition diagnosis in a hospital setting. This study compares the diagnostic performance of this approach that uses the Nutritional Risk Screening-2002 (NRS-2002) as a screening tool and the direct application of GLIM malnutrition diagnostic criteria in hospitalized patients. This cross-sectional study involved 290 adult and older adult patients who were hospitalized. A trained nutritionist implemented the two-step GLIM approach, including NRS-2002 (in the first step) and GLIM criteria (in the second step) for each patient. Then, the accuracy, kappa index, area under the receiver operating characteristic curve (AUC ROC), sensitivity, and specificity of malnutrition diagnostic performance of the two-step GLIM approach and NRS-2002 were evaluated compared to thedirect use of GLIM criteria. The NRS-2002 identified 145 (50.0%) patients as at risk of malnutrition. The prevalence of malnutrition using the two-step GLIM approach and GLIM malnutrition diagnosis criteria were 120 (41.4%) and 141 (48.6%), respectively. The kappa index showed substantial and almost perfect agreement for NRS-2002 (κ = 68%) and the two-step GLIM approach (κ = 85%) with GLIM malnutrition diagnostic criteria, respectively. Furthermore, the AUC ROC (0.926; 95% confidence interval (CI): 0.89-0.96) and accuracy (92.8%) of the two-step GLIM approach compared to the GLIM criteria indicated an acepptable ability to distinguish between malnourished and well-nourished patients. The two-step GLIM approach using NRS-2002 as a screening tool (in step one) had acceptable malnutrition diagnostic performance compared to the direct application of GLIM criteria in hospitalized patients.