A cross-sectional study was undertaken to determine the nutritional status based on Body Mass Index (BMI) and Mid Upper Arm Circumference (MUAC) of adult Santals of Jhargram District, West Bengal, India. A total of 348 (173 male and 175 female) adults (aged ≥18 years) Santals of two villages in Jhargram District (approximately 155 km from Kolkata) were studied. Some Anthropometric measurements (Height, Weight and MUAC) and age-sex were taken using standard protocols. Overall, the extent of Chronic Energy Deficiency (CED) (BMI<18.5 kg/m2) was found to be fairly high (33.6%). The prevalence of CED (based on BMI) was higher in females (36.6%) compared to males (30.6%). Using World Health Organization (WHO) Criterion (WHO, 1995), the prevalence of undernutrition (based on BMI) was high and the situation was critical. Similarly, the extent of undernutrition (based on MUAC) was found to be fairly high (30.7%). The prevalence of undernutrition (based on MUAC) was higher in males (31.2%) than females (30.3%). In conclusion, this study provided evidence that the prevalence of adult Santals undernutrition (Both BMI & MUAC) was high. Thus, immediate appropriate nutritional intervention programs need to be implemented for this tribal population. Moreover, further research is needed not only among this ethnic group but also among all ethnic groups in India to find out the causes and consequences of adult undernutrition.