Mangroves are globally recognized for their ecological, social, economic, and cultural significance. In recent years, data and assessment on carbon storage in tropical forests including mangroves have significantly improved. However, site-specific evidence as in the case of tropical islands and low-lying coastal zones where climate change effects are likely to be severe is lacking. This paper evaluates the change of carbon stock and its spatial variation in the mangrove ecosystems of Andaman Islands in India. The study highlights the mangrove cover change (2005–2019) and systematically reviews the variation in aboveground biomass of mangrove ecosystems in Southeast Asia. The results showed that the mangrove cover significantly decreased from 2005 to 2010, largely due to the Indian Ocean tsunami and geomorphic changes associated with tectonic processes in the islands. The dense mangrove cover had declined by 92 km² between the years of 2005 and 2010 and then increased by 37 km² between the years of 2010 and 2019. The average aboveground vegetation carbon stock of mangroves was found to be 86.41_Mean ± 59.82_SD t C ha⁻¹. In regard to ecosystem service, the monetary value of AGB carbon stock is an estimated US$424.62 million. The map developed from this study delivers a valued tool for assessing carbon stocks and highlighting priority areas for conservation, EbA Ecosystem Based Adaptation, and restoration interventions. The present study also addresses the knowledge gap present in the ecosystem service dimensions of a major mangrove system in India, which can contribute to reliable and informed decision-making in mangrove management.