Background Estimating malnutrition risk among hospitalized patients is challenging, yet critical due to its association with adverse outcomes such as prolonged hospital stays, increased mortality, impaired wound healing, depression, and increased hospital costs. This research study aims to evaluate the risk of malnutrition among type 2 diabetic hospitalized patients and its impact on the patient’s length of stay in two tertiary hospitals based in Kigali. Method In this retrospective cross-sectional study, 300 adult hospitalized type 2 diabetic patients from Kigali’s tertiary hospital and King Faisal Hospital were enrolled between January 2021 and October 2022. Data collected includes demographics, anthropometrics, serum albumin, and length of hospital stay. The Nutrition Risk Index was used to determine malnutrition risk. Results 55.3% of hospitalized type 2 diabetes patients were found to be at risk of malnutrition based on the Nutrition Risk Index. Gender distribution showed no significant difference (p = 0.724), with 56.6% females and 54.5% males at risk. Significant associations were found with age (r=0.018, p= 0.017), hypertension as comorbidity (r=-0.169, p = 0.004), hospital stay duration (r=0.139, p= 0.016), and blood glucose levels (r=-0.087, p = 0.001). Conclusion A study finds high malnutrition risk in hospitalized type 2 diabetes patients, linked to longer stays and poor outcomes. Early malnutrition screening, proper nutrition support, and a multidisciplinary care team are crucial for improved clinical care and cost-effectiveness.