This article analyzes the determinants of international child adoption. We argue that prospective parents’ desire to reduce transaction costs and ensure a successfully completed adoption influences adoption flows. Drawing on dyadic panel data over the period 1991–2010, we fit hurdle models to identify sending-country and dyad characteristics that correlate with adoption flows. We show that an international agreement designed to ensure the integrity of adoption depresses foreign adoptions by raising transaction costs. By contrast, adoption is more likely when sending countries have a high-quality regulatory environment and when colonial or migration ties exist within the dyad. Our findings highlight the impact of transaction costs on transnational, non-market exchange, expand political economy models of migration, and emphasize the importance of private international law in international relations.