Objectives. Although tribals constitute around 8.6% of the total population of India, detailed information on their body composition is scanty. Thus, our objective was to evaluate age variations and sexual dimorphism in adiposity and body composition among rural tribal adolescents of Kharagpur, West Bengal, India. Material and methods. This cross-sectional study was conducted among 788 tribal adolescent boys and girls, aged 10-17 years of Kharagpur, West Midnapore, West Bengal, India. Height (kg), weight (cm) and skinfolds were measured following standard method. The Body Mass Index (BMI) was derived. Body composition measures including Percent Body Fat (PBF), Fat Mass (FM), Fat Free Mass (FFM), Fat Mass Index (FMI) and Fat Free mass Index (FFMI) were computed using standard equations. Results. All the variables showed a significant age trend in both sexes. Age-combined significant sex differences existed in mean BMI and all body composition measures. Girls had significantly higher mean values of fat measures (PBF, FM and FMI) whereas boys had significantly higher mean values of non-fat measures (FFM and FFMI). In both sexes, age had significant correlations with BMI and the five body composition measures. Similarly, all body composition indicators were significantly correlated with BMI in both sexes. Conclusions. There were significant age and sex variations in body composition measures. Girls had significantly more fat mass whereas boys had more lean body mass. All body composition measures increased significantly with increasing age as well as BMI. Attainment of puberty could be a mediating factor causing these age variations and sexual dimorphism. Keywords: India, tribal adolescents, age variations, sexual dimorphism, body composition.