Each year the United States resettles thousands of refugees in pre-determined locations across the country. However, refugees are free to relocate upon arrival. Although this secondary migration can fundamentally alter outcomes for both refugees and the communities that host them, policymakers lack systematic data on this phenomenon. Using novel administrative data covering all adult refugees resettled between 2000 and 2014 (N≈447,000), we provide a comprehensive analysis of secondary migration patterns. A high proportion of refugees leave their initial resettlement site and migrate to a different state, although rates vary widely by origin, family ties, and arrival state. Importantly, secondary migration is driven primarily by the presence of co-ethnic networks and labor market considerations. We find no evidence that patterns of secondary migration are driven by state partisanship and the generosity of welfare benefits.