Background: Following the improvement in health status and life expectancy in developing countries, the elderly population is increasing. Elderly malnutrition is common across healthcare services and is associated with high costs and adverse outcomes. This study assesses the prevalence of malnutrition among elderly patients in the selected hospitals affiliated to Tehran University of Medical Sciences. Methods: This cross-sectional study was conducted on elderly patients aged 65 years or older in 6 selected hospitals between June and September 2015. Using convenience sampling method, a total of 451 patients were included. Nutritional status was assessed using the Mini Nutritional Assessment (MNA) tool. Results: The mean age of the patients was 71.49 ± 6.60 year and 55.5% were female. The prevalence of malnutrition was 27.3%. A total of 30.8% were at risk of malnutrition, and 41.9% had a normal nutritional status. There were significant associations between nutritional status and chronic diseases, body mass index (BMI), mobility, psychological condition, mid-arm circumference (MAC), calf circumference, and more than three prescription drugs per day (P < 0.001). Conclusion: A satisfactory nutritional status was found among most hospitalized elderly. Future studies with follow-up during and after hospitalization are required.