Wetland ecosystems, particularly coastal vegetated ecosystems, play a vital role in climate mitigation and adaptation. Coastal vegetated habitats (including coastal wetlands such as seagrass meadows, saltmarshes, and mangroves) are some of the most efficient ecosystems for storing carbon on a per hectare basis, retaining organic carbon for centuries to millennia. We conducted carbon stock assessments, to a depth of 1 m, across four young saltmarsh sites and the adjacent mudflats in Dublin, Ireland. Soil cores and vegetation samples were taken across each site in order to analyze the carbon content of each carbon pool. The carbon density of Dublin’s saltmarshes was 112.1 ± 10.1 Mg C _org ha^{− 1} . The dominant plant species were Spartina anglica, Plantago maritima, and Atriplex portulacoides. The soil carbon pool of these saltmarshes contributes 87% to the total carbon stock, with living plant biomass contributing the remaining 13%. Saltmarshes are important ecosystems for climate mitigation and can provide nature-based solutions to reduce net carbon emissions; however, their degradation will lead to the loss of climate-relevant carbon pools.