Domestic strife and civil war frequently produce large population dislocations and refugee flows across national boundaries. Mass refugee flows often entail negative consequences for receiving states, particularly in developing countries. Moreover, civil violence frequently extends across national boundaries as “internal” conflicts are not constrained by borders. This article argues that refugee flows between states significantly increase the likelihood of militarized interstate disputes (MIDs) in that dyad. Refugee-receiving states are more likely to initiate MIDs as they intervene to prevent further externalities, and refugee-sending states initiate MIDs as they violate borders in pursuit of dissidents. Moreover, this research challenges conventional theories of international conflict that focus exclusively on distributional bargains between states. These propositions are tested in a quantitative analysis of the relationship between refugees and MID initiation, 1955–2000. Results confirm that refugees significantly increase the probability of international conflict.