Undernutrition is a major underlying problem among the population of the low-middle income countries including India. The prevalence of undernutrition is increasing amongadolescents. The present cross-sectional study will determine the prevalence of thinness among the adolescents (10-17 years) of Nandigram, PurbaMedinipur using the cut off given by Cole et al. (2007). This study will also find the association of different socio-economic and demographic variables on the same. Sample size for the present study was 958. The prevalence of overall thinness was 44.48% and 35.37% among the boys and girls respectively. The result of binary logistic regression analysis showed that gender, number of siblings, house type, physical exercise, midday meal consumption, parental education, parental occupation, family income and menarcheal status were significantly associated with thinness. Proper awareness related to nutritional requirement, eating habits and lifestyle would be helpful to reduce the prevalence of undernutrition among adolescents.