The carbon dynamics of forest ecosystems are particularly significant to the phenomenon of global warming. Mangrove forests situated between aquatic and terrestrial ecosystems show unique patterns of biomass allocation and carbon dynamics, as they are subjected to daily tidal inundations and a mixture of seawater and fresh water. Due to the recent decrease in areas of mangrove forests, their carbon dynamics should be re-examined and updated. The estimation of net ecosystem productivity (NEP) is an approach for studying the carbon dynamics of an ecosystem. In this review, we performed an NEP estimation of mangrove forests in tropical and subtropical regions. The magnitude of estimated NEP was compared by two methods: the summation method and the eddy covariance technique. We found that a possible under-estimation in the summation method occurs if the belowground litter production is excluded from measurements. We also confirmed high NEP trends of mangrove forests in a comparison to upland forests. In summary, the mangrove ecosystems are considered a significant carbon sink in the tropics.