This chapter uses a rational choice approach to examine the political economy of terrorist financing. To date, much of the theoretical literature and almost all government-sponsored reports discuss terrorist organizations as though they are made up of ideologically driven purists who share a uniform commitment to the cause. This assumption is needed to explain how these organizations can both (1) efficiently distribute funds and (2) operate covertly without the checks and balances most organizations require. However, upon closer inspection, one often sees substantial differences in the preferences of key players in terrorist networks. Two selection processes explain why these differences exist, and a principal-agent framework shows how these differences lead to inefficiencies in terrorist financial systems. Terrorist organizations face a trade-off between enduring the inefficiency or employing corrective strategies that create vulnerabilities. Governments can undertake specific actions to make this trade-off more problematic.