Coastal cities of Caribbean and Pacific Small Island developing states (SIDS) are highly vulnerable and will be among the earliest and most affected by climate change in the coming decades. Approximately 29 million people reside in Caribbean and Pacific SIDS, 4.2 million of which reside in low-elevation coastal zones (LECZs) located less than 10 meters above the sea level. The cost of damage to critical infrastructure that supports human settlements along the coast that results from rising sea levels will be a financial burden to many SIDS. By 2100, the cost of rising sea levels as a percentage of GDP will be highest amongSIDS and enormous relative to the size of their economies. Impacts could include a decline in national output, inflation, increasing debt, revenue loss, and employment decline. Adapting and improving the resilience of cities in coastal zones of SIDS, especially those experiencing rapid urbanization, remains critical.