Journal ArticleThe study assessed carbon stocks of Hanang mountain forest, Tanzania. Thirty-four sample plots (40 × 50 m) were established along an altitudinal gradient. All trees with diameter at breast height ≥10 cm were identified and measured, and herb species and soil were sampled from four 1 × 1 m quadrats -1 within 10 × 10 m subplots. Mean carbon stock was 48.37 and 0.26 t C ha for tree and herb species, -1 respectively. Soil organic carbon (SOC) was 64.2, 41.93 and 31.0 t C ha in the upper, mid and lower layers, respectively. It was found that there was significant difference in tree carbon (p<0.05) along an altitudinal gradient. However there was no significant difference (p>0.05) in herbaceous carbon and SOC in the three layers along an altitudinal gradient. Tree carbon was low compared to other tropical areas where allometric models were employed. In contrast, SOC was high compared to other similar forests in the tropics. Anthropogenic threats will likely diminish the SOC hence conservation measures are needed.