Background The Global Leadership Initiative on Malnutrition (GLIM) has the potential to gain global acceptance for diagnosing malnutrition. Of which, calf circumference (CC) was proposed as an alternative to evaluate the reduced muscle mass (RMM). The present study aimed to evaluate whether including the hand grip strength (HGS) was helpful for diagnosing malnutrition under the GLIM framework. Methods We performed a multicenter, observational cohort study including 3998 patients with cancer at two teaching hospitals. The RMM criterion was separately assessed using the calf circumference (CC), or the CC and HGS combined. Accordingly, two methods of GLIM diagnosis were independently developed to determine the nutritional status of the patients. The diagnostic concordance, baseline characteristics, and outcomes of patients were compared across the malnourished-CC-HGS, malnourished-CC+HGS, and well-nourished groups. The Patient-Generated Subjective Global Assessment (PG-SGA) was used as a comparator to identify the optimal method. Results Malnutrition was identified in 1120 (28%) patients by the CC method and 1060 (26.5%) patients by the CC+HGS method. Compared to the well-nourished group, the malnourished-CC+HGS group (60 patients, 1.5%) had poorer nutritional characteristics, poorer Karnofsky Performance Status scores, poorer global quality of life scores, and higher Nutritional Risk Screening 2002 scores. The severity of malnutrition diagnosed using the CC method (Kappa = 0.136) showed higher agreement with the PG-SGA than the CC+HGS method (Kappa = 0.127). Conclusion Compared to CC+HGS, the CC alone appears to be adequate to evaluate RMM under the GLIM framework. A simpler method might facilitate the application of these criteria in clinical settings by increasing efficacy and minimizing missed diagnoses.