Forest plays an important role on reducing the impact of global warming as carbon sink. Forest has an ability to absorb carbon on large scale and store it as biomass. This research was aimed to determine the potential of aboveground biomass and carbon stock in pine-mahogany mixture stands in KHDTK Gunung Bromo. The systematic sampling with random start was used to determine the plot, and the distance between plots were 100 m. In total, there were 35 square plots, 20 × 20 m in size, that had been set up under the pine-mahogany mixture stands. This research was conducted by using non-destructive sampling method by measuring the tree diameter at breast height. The diameter ranges of pine and mahogany were 10-70 cm. Tree biomass was estimated by allometric equations. The result showed that biomass and carbon stock in pine stands were 113.84 ton/ha and 53.50 ton C/ha while for mahogany stands were 32.06 ton/ha and 15.07 ton C/ha. Thus, the total biomass and carbon stock in pine-mahogany mixture stands were 45.90 ton/ha and 68.57 ton C/ha.