During 2020, extensive mangrove die-back occurred on multiple islands in the Maldives which is the lowest elevated nation on Earth and where mangroves provide crucial resources and shoreline protection. The dieback event coincided with both an extreme positive Indian Ocean Dipole event and the highest sea level on tide gauge records. Using a combination of remote sensing, dendrology and sediment geochemistry we observed a significant decrease in Normalized Difference Vegetation Index after the Indian Ocean Dipole event, increased salinity in dead tree wood chronologies and relative sea level rise up to four-fold higher than the mangrove sediment accretion rates. Coral reef island mangrove forests are especially vulnerable to the intensification in sea level rise due to low elevation, limited sediment supply, and small land size. However, large dieback events at these sites related to sea level have not been previously documented. Our multiple lines of evidence suggest the forest was inundated and unable to keep pace with rising sea levels, leading to tree mortality. The findings from the Maldives serve as a precursory warning to mangroves forests in Small Island Developing States.