It is important to detect and treat malnutrition in hospital patients so as to improve clinical outcome and reduce hospital stay. The aim of this study was to develop and validate a nutrition screening tool with a simple and quick scoring system for acute hospital patients in Singapore. In this study, 818 newly admitted patients aged above 18 years old were screened using five parameters that contribute to the risk of malnutrition. A dietitian blinded to the nutrition screening score assessed the same patients using the reference standard, Subjective Global Assessment (SGA) within 48 hours. Sensitivity and specificity were established using the receiver operator characteristics (ROC) curve and the best cut-off scores determined. The nutrition parameter with the largest area under the ROC curve (AUC) was chosen as the final screening tool, which was named the 3-Minute Nutrition Screening (3-MinNS). The combination of the parameters weight loss, intake and muscle wastage (3-MinNS), gave the largest AUC when compared with SGA. Using 3-MinNS, the best cut-off point to identify malnourished patients is three (sensitivity 86%, specificity 83%). The cut-off score to identify subjects at risk of severe malnutrition is five (sensitivity 93%, specificity 86%). The 3-Minute Nutrition Screening is a valid, simple and rapid tool that identifies acute hospital patients at risk of malnutrition in Singapore. It is able to differentiate patients at risk of moderate malnutrition and severe malnutrition for prioritization and management purposes.