Low-lying atoll islands are especially threatened by anticipated sea-level rise, and migration is often mentioned as a potential response of these island societies. Further, small island states are developing population, economic and adaptation policies to plan the future. Policies, such as raising of islands or land reclamation, require a long-term vision on populations and migration. However, population and migration systems in small island settings are poorly understood. To address this deficiency requires an approach that considers changing environmental and socio-economic factors and individual migration decision-making. This article introduces the conceptual model of migration and explores migration within one small island nation, the Maldives, as an example. Agent-based simulations of internal migration from 1985?2014 are used as a basis to explore a range of potential demographic futures up to 2050. The simulations consider a set of consistent demographic, environmental, policy and international migration narratives, which describe a range of key uncertainties. The capital island Malé has experienced significant population growth over the last decades, growing from around 67,000 to 153,000 inhabitants from 2000 to 2014, and comprising about 38 percent of the national population in 2014. In all future narratives, which consider possible demographic, governance, environmental and globalization changes, the growth of Malé continues while many other islands are effectively abandoned. The analysis suggests that migration in the Maldives has a strong inertia, and radical change to the environmental and/or socio-economic drivers would be needed for existing trends to change. Findings from this study may have implications for national development and planning for climate change more widely in island nations.