The increase of the organic carbon in the environment that was not followed by carbon adsorbents will trigger climate change that contributes to global warming. The mangrove forest is the ecosystem that can absorb carbon emission from the environment and reserve it in its leaves, stems, and sediment. This research aimed to show the information related to the estimated organic carbon value stored in the mangrove forest’s sediments on Dompak Island. This research was conducted in December 2020 at Dompak Island, Riau Islands. Carbon stock data was evaluated using the LOI (Loss On Ignition) method. The sediment specimens were collected from 5 stations. The result showed that the north station has the highest carbon content, 443.1 tons C/ha, and the south station has the lowest carbon content, 223.65 tons C/ha. The result from the statistic analysis using a one-way ANOVA test between the locations showed that the organic value carbon content in Dompak Island with the significance value of 0.05 stated that there is no real difference.