We provide evidence for the existence of spillover effects of national immigration policies by estimating the effect of stricter family reunification rules in Denmark on migration behavior. We reach three main conclusions. Using Danish register data, we first show that stricter rules for reunification led to a clear and significant increase in emigration of Danish citizens with immigrant background. Most of the emigrants left Denmark for Sweden, a neighboring country in which reunification was possible. Next, using Swedish register data, we find that affected individuals emigrating to Sweden actually came for family formation purposes. Finally, we demonstrate that not all individuals that came to Sweden to reunite with a partner stayed in the country; of those leaving, return migration to Denmark was most common. Our results indicate that potential spillover effects from national migration policies should be taken into account when forming migration policy.