The IDB has 26 borrowing member countries, all of them in Latin America and the Caribbean. Together, they have slightly more than 50 percent of the voting power on the IDB board (see capital stock and voting power ).

Since the IDB’s Ninth General Capital Increase (IDB-9), the IDB has aimed to dedicate at least 35 percent of its annual lending approval volume to the small and vulnerable countries in the region, which include the following: Bahamas, Barbados, Belize, Bolivia, Costa Rica, the Dominican Republic, Ecuador, El Salvador, Guatemala, Guyana, Haiti, Honduras, Jamaica, Nicaragua, Panama, Paraguay, Suriname, Trinidad and Tobago and Uruguay. The remaining borrowing member countries include Argentina, Brazil, Chile, Colombia, Mexico, Peru, and Venezuela.