Previous studies investigating the health consequences of migration often face difficulties choosing a proper comparison group and tackling the problems of potential endogeneity and self-selection bias. Using propensity score matching difference-in-differences and an instrumental variable approach, this paper examines the impact of internal migration on the health of rural migrants in China. We find robust evidence of a significant negative effect of internal migration on rural migrants’ health. We also find significant heterogeneity in the impact across different age groups. Younger migrants aged between 16 and 35 are most likely to experience health decline following migration. In addition, we find that the key mechanisms through which internal migration affects the health of rural migrants are the changes in emotional state and social trust.