Mangrove forests are incredibly effective and significant carbon sinks, with the potential to absorb more carbon than other terrestrial forests. However, over time, the forests are subjected to severe environmental conditions such as land use change and unclear impact on carbon sequestration. The study about “Quantification of Aboveground Carbon Sequestration in Delta Tumpat Mangrove Forest” through five islands aims to assess carbon stock and to quantify aboveground carbon sequestration in Delta Tumpat Mangrove Forest. The method that were used such as measuring DBH and height, also with calculation of carbon stock, carbon sequestration and the basal area, tree volume and tree per hectare. A total of 155.29 tanC/ha and 18.96 tanC/ha/year are shown in the data, which was collected from five islands: Pulau Mas, Pulau Tujuh, Pulau Layang-Layang, Pulau Bedal A, and Pulau Bedal B. Pulau Bedal B has the greatest carbon stock of the five islands, 4.91 tanC/Ha/year, due to its planted areas, which have been there for nine years. The outcome was impacted by the gradual deterioration and reduction of factors including precipitation and soil pH.