Forests play a significant role in climate change mitigation by sequestering and storing carbonrnfrom the atmosphere which was released by anthropogenic factors. The overall objective of thisrnstudy was to estimate Carbon stock of above and below ground biomass along altitudinalrngradient in the woodland vegetation (Ilu Gelan District, Oromia Region). The study was usedrnallometric models equation of Brown et al. (1989) for above ground and below ground biomassrnwas calculated based on the ratio of below ground biomass to above ground biomass ratio ofrn(MacDicken,1997) using systematic transects line sampling to estimate the above groundrnbiomass data for different trees with diameter â‰¥5 cm found in the study area. Quadrants of 54rnplots were established by dropping a distance of 25 m altitudinal gradient between each plotrnwith square plots of 400 m2 (20 m x 20 m). Parameters such as the diameter at breast heightrn(DBH) and height were used. A total of 86 woody species of 39 families with stem number ofrn4188 was collected and analyzed. The results of this study showed that the total mean carbonrnbiomass in 54 plots of the study was 87.77 C t /ha for above ground biomass (AGB) and 17.5 Crnt/ha for below-ground biomass (BGB). In this woodland ecosystem, the total mean carbon stockrnof AGC was more important compared to the total carbon stock of BGC which was 41.25 t C /harnagainst 8.25 t C/ha respectively. Similarly, the average carbon stock of lower altitude was largerrnthan that of the higher altitudinal gradient with the same pattern of AGB and BGB (183.23,rn60.49C t C/ha) respectively. This result showed that the species density is larger at higherrnaltitude when compared to the lower altitude because of different anthropogenic disturbancesrnand threats in the study area. This research indicates that, this woodland vegetation holds largernstores of carbon, yet uncertainty remains regarding their quantitative contribution to globalrncarbon cycle.rnKey words: Above ground biomass, Altitudinal gradient, below ground biomass, Carbon stock,rnMountain Dirki woodland.