Nutrition screening is recommended as a first step of nutrition care to allow early identification and intervention of malnourished patients. The present study determined the validities and reliabilities of two malnutrition screening tools namely, the Malnutrition Universal Screening Tool (MUST) and Malnutrition Screening Tool (MST) among adult patients at the Hospital Kuala Lumpur. Methods: The sensitivity, specificity and predictive value of MUST and MST were conducted against the Subjective Global Assessment (SGA), anthropometric parameters including body mass index (BMI), calf circumference (CC),mid-upper arm circumference (MUAC) and energy intake. Inter-rater reliability was evaluated using kappa value (κ) to determine the level of agreement between raters. Results: A total of 151 subjects with mean age of 45.2 ± 13.7 years participated in this study. Prevalence of malnutrition according to MUST, MST and SGA was 34.4%, 33.8% and 19.9%, respectively. As compared to SGA, MUST and MST had a sensitivity of 96.6% and 93.3% respectively, whereas the specificity was 80.9% for both tools. The sensitivity and specificity of MUST against the anthropometric parameters (BMI, CC and MUAC) were between 53.8% to 88.8% and 67.4% to 69.9%, respectively. The sensitivity values for MST were between 46.1% to 63.6% and specificity values were between 64.4% to 67.6%. The inter-rater reliability of MUST was higher (substantial, mean (κ) = 0.78) than for MST (moderate, mean (κ) = 0.52). Conclusions: In conclusion, MUST was found to have similar validity levels but higher reliability result than MST. Based on our result, MUST is recommended for use in identifying adult patients who are at high risk of malnutrition. It can be used as a malnutrition screening tool but there is a need to evaluate the cost effectiveness of its implementation.