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Mangroves are well-known for their numerous ecosystem services, including storing a globally significant C pool. There is increasing interest in the inclusion of mangroves in national climate change mitigation and adaptation plans in developing nations as they become involved with incentive programs for climate change mitigation. The quality and precision of data required by these programs necessitates the use of an inventory approach that allows for quantification, rather than general characterization, of C stocks. In this study, we quantified the ecosystem C stock of the Zambezi River Delta mangroves utilizing a rigorous, yet operationally feasible approach. We applied a stratified random sampling inventory design, based on five forest canopy height classes, derived from Ice, Cloud, and Land Elevation Satellite/Geoscience Laser Altimeter System (ICE Sat/GLAS) and the Shuttle Radar Topography Mission (SRTM) data, and a Spatial Decision Support System to allocate inventory plots. Carbon content in above- and below-ground biomass pools in addition to soils to a depth of 200 cm was measured. The average biomass C density for the height classes ranged from 99.2 Mg C ha-1 to 341.3 Mg C ha-1. Soil C density was the largest measured C pool, containing 274.6 Mg C ha-1 to 314.1 Mg C ha-1 and accounting for 45–73% of the height class ecosystem C densities, which ranged from 373.8 Mg C ha-1 to 620.8 Mg C ha-1. The ecosystem C density estimates for the five strata were weighted based on their spatial distribution across the landscape to yield a total C stock for the Zambezi River Delta mangroves of 1.4 × 107 Mg C. The error bounds from the 95% confidence interval are ±6% of our ecosystem C stock estimate, well within acceptable levels of uncertainty.