Undernutrition is a major concern particularly for the tribal people who are living in remote areas. For last two decades neck circumference (NC) is being used as an alternative tool to access obesity and over weight for Body Mass Index (BMI). But scholarly works regarding the use of neck circumference to evaluate undernutrition are not available till the date. The aim of this pioneering study is to find out the efficacy of neck circumference to determine undernutrition among Indian adults. A cross-sectional study was conducted among 198 adult Sabar males in the Purulia District of West Bengal, India. Anthropometric variables like height (cm), weight (kg), neck circumference (cm) were measured and BMI (kg / m2) was calculated. One way ANOVA and Pearson’s correlation were performed and Receiver Operating Characteristics (ROC) curve analysis was done to find out best cut off threshold of neck circumference against BMI. P value of ≤0.05 was considered statistically significant. Results revealed that BMI was better correlated to neck circumference (r= 0.616) than weight. NC 32.65 cm (AUC 0.792; 95% CI= 0.724-0.861) may be regarded as best cut off for determining undernutrition (BMI<18.5 kg/m2) among adult Sabar males. In the context of this study, neck circumference showed significant association with BMI for community based screening of undernourished subjects. Neck circumference is a feasible method to identify adult malnutrition. Thus NC might be considered as a screening tool for malnutrition and key nutritional status indicator among the tribal population.