Spatial understanding of biomass and carbon stock in tropical moist deciduous forests is crucial in assessment of global carbon budget. The present study was aimed to assess the above ground and below ground carbon stock and its relation with tree diversity parameters in two tropical moist deciduous forest sites, namely: Xylia dominated forest (XDF) and Sal dominated forest (SDF) of Similipal Biosphere Reserve (SBR), Odisha, India. A total of seventy-two tree species ≥ 5 cm diameter at breast height (dbh) were recorded, belonging to 62 genera and 27 families. Estimated average above-ground biomass carbon and soil organic carbon were 180.05 Mg C ha−1, 55.4 Mg C ha−1 and 209.3 Mg C ha−1, 61.8 Mg C ha−1 in XDF and SDF of SBR, respectively. Shorea robusta Gaertn. was the most carbon accumulating species of both the forests contributing about 21.5% of biomass carbon in XDF and 47.8% biomass carbon in SDF. Maximum carbon allocation was in above-ground biomass pool (69.04%) followed by soil organic carbon (20.9%) and below-ground biomass/root (10.1%). The correlation study revealed that above-ground biomass had strong positive correlation with basal area and Importance Value Index of tree species indicating importance of dominant species in carbon storage. Therefore, the dominant tree species such as S. robusta Gaertn., Xylia xylocarpa (Roxb.) Taub., Terminalia tomentosa Wight & Arn., Schleichera oleosa Lour.) Merr. etc. is suggested for proper conservation and management to maintain the carbon stock of SBR. The results emphasized the importance of tropical moist deciduous forests in potential carbon storage and conservation of biodiversity in forest ecosystem of India. Further, the information will supplement to the global deficit of carbon stock data of moist deciduous forest and has implications in carbon model projections and management both nationally and globally.