Shocks to net migration matter for the business cycles of some countries. Using an estimated dynamic stochastic general equilibrium (DSGE) model of a small open economy and a structural vector autoregression, we find that migration shocks account for a considerable proportion of the variability of per capita GDP. Migration shocks matter for the capital investment and consumption components of per capita GDP, but they are not the most important driver. Migration shocks are also important for residential investment and real house prices, but other shocks play a larger role in driving housing market volatility. In the DSGE model, the level of human capital possessed by migrants relative to that of locals materially affects the business cycle impact of migration. The impact of migration shocks is larger when migrants have substantially different levels of human capital relative to locals. When the average migrant has higher levels of human capital than locals, as seems to be common in most OECD economies, a migration shock has an expansionary effect on per capita GDP and its components.