Using the quasi-random allocation of refugees and detailed administrative data, we examine the effect of urban density on refugees’ decisions to naturalise. Our results indicate that refugees assigned to urban areas are more likely to naturalise, largely due to a higher density of co-national networks. We find that a one standard deviation increase in co-national density increases the likelihood of naturalising by 1.3 percentage points. Our findings remain robust even after accounting for factors such as labour market effects and public attitudes and seem to stem from the reduced information costs and strength of weak ties within co-national networks.