The present study aims to determine the prevalence of chronic energy deficiency (CED) amongst adult Santhals. A cross sectional sample of 1262 adult Santhals (692 males and 570 females) were collected from West Bengal using multistage cluster random sampling. Body mass index (BMI) has calculated for each subject and categorized according to WHO classification. Linear regression has been computed to assess the effect of various socio-economic factors on nutritional status, which is estimated from BMI. Nutritional status of Santhals suggests high prevalence (46.9%) of undernutrition (BMI < 18.50 kg/m2) in this population, which is more apparent in females (50.0%) as compared to their counterparts (44.4%). Negative and statistically significant coefficient of age2 on BMI reflects that with the increase in age, effect of age on BMI increases. This results into a low BMI with increment of age. Economy has a crucial role in developing low BMI among Santhals (β = -1.194±0.171, p<0.01). Undernutrition is an increasing problem in West Bengal, especially in tribal communities. Poor socio-economic condition and necessity of doing labourious physical activity to sustain daily livelihood affects body mass index of these tribal people.