Economic growth in developing countries has potentially countervailing effects on international migration. Higher income at home not only narrows wage gaps with rich countries but also relaxes liquidity constraints that may have prevented migration among the poor. To understand which effect predominates, we must first know to what extent financial barriers limit international migration from low-income settings. To answer this question, I develop and test a model of migration flows with fixed migration costs and imperfect credit markets. By allowing for idiosyncratic wealth heterogeneity and differentiating between transitory and permanent income shocks, I obtain testable implications not available in existing models of migration. Borrowing insights from recent trade literature, I propose a novel and empirically tractable method for aggregating individual migration choices. These closed-form expressions make it possible to identify the presence and magnitude of liquidity constraints using aggregate migration data. After constructing a new panel dataset on temporary international migration rates from over 65,000 Indonesian villages, I test for liquidity constraints using household-level land-holdings heterogeneity, rainfall shocks, and a large exogenous increase in domestic rice prices with considerable spatial variation. Positive agricultural income shocks are associated with significant increases in the share of village residents working abroad. These increases are larger in villages with lower mean and less dispersion in land-holdings. The empirical findings are consistent with binding liquidity constraints in the model, and I provide additional evidence supporting this interpretation.