Background and Aim: Malnutrition is a prevalent health problem but an unknown one to which little attention has been paid. This can increase complications, morbidity and mortality of the disease. Therefore, early detection of malnutrition to provide nutritional support for patients is very crucial. The main objective of the present study was to determine the nutritional status of patients admitted to the hospitals affiliated to Birjand University of Medical Sciences (BUMS). Materials and Methods: This cross-sectional study on patients admitted to five hospitals affiliated to BUMS was done in 2011. Through stratified random sampling, 549 patients older than 20 years were selected from five hospitals and their nutrition status was determined by means of measuring their height, weight, and body mass index according to Malnutrition Universal Screening Tool (MUST) on their admission. The obtained data was analyzed by SPSS (V:16), using X2 at the significant level P <0.05. Results: Mean age of the patients was 49 ±20 years. Among them, 52.8% were males. Prevalence of malnutrition was 58.8% from which 53 % were at high risk and 5.8 % at medium risk. Among the patients, 148 (57.1% female patients were at high risk of malnutrition whereas, in the males the high risk was diagnosed in 143 (49.3%) which the difference was significant (men) (P=0.03). Prevalence of malnutrition in citizens was higher than villagers (P=0.001). It was also significantly higher in over 45 year olds compared to other age groups (P=0.04). Conclusion: Malnutrition is a common problem from which more than 53 % of the patients suffer. Therefore, an organized clinical nutritional service in the health centers are required.