This paper takes a sustainable livelihoods approach to understanding the relationship between migration and poverty, and it explores the effects of poverty on people's decision and ability to migrate. The paper argues that poverty and vulnerability have two conflicting effects on migration: by providing incentives to migrate, either as a strategy for livelihood diversification or out of destitution; but also by reducing the ability to migrate because the transfer costs involved, in terms of financial, human, physical and social capital, are too high.