|Argentina* ^||Ecuador* ^||Nicaragua* ^|
|Austria*||El Salvador* ^||Norway*|
|Bahamas* ^||Finland*||Panama* ^|
|Barbados* ^||France*^||Paraguay* ^|
|Belize* ^||Guatemala* ^||Portugal*^|
|Bolivia* ^||Guyana* ^||Slovenia|
|Brazil* ^||Haiti*^||Spain* ^|
|China, People's Republic of* ^||Italy* ^||Switzerland*^|
|Colombia* ^||Jamaica* ^||Trinidad and Tobago* ^|
|Costa Rica* ^||Japan* ^||United Kingdom ^|
|Croatia||Korea, Republic of* ^||United States* ^|
|Denmark*||Mexico* ^||Uruguay* ^|
|Dominican Republic* ^||Netherlands* ^||Venezuela* ^|
|* Member of the Inter-American Investment Corporation|
|^ Member of the Multilateral Investment Fund|
The IDB was founded in 1959 as a partnership between 19 Latin American countries and the United States. The original member countries were Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, the Dominican Republic, Ecuador, El Salvador, Guatemala, Haiti, Honduras, Mexico, Nicaragua, Panama, Paraguay, Peru, Uruguay, Venezuela and the United States.
Over the next several decades, the Bank expanded its membership, initially through the Western Hemisphere. Trinidad and Tobago became a member in 1967, to be soon joined by Barbados (1969), Jamaica (1969), Canada (1972), Guyana (1976), The Bahamas (1977) and Suriname (1980). The 22 non-regional or non-Western Hemisphere member countries, consisting of 16 European states plus Israel and Japan, joined between 1976 and 1986. Belize became a member in 1992 and Croatia and Slovenia joined as successor states of Yugoslavia in 1993. The Republic of Korea became a member country in 2005 and the People's Republic of China became a member country in 2009.
Cuba signed but did not ratify the Agreement Establishing the Bank, the institution’s charter, so it has not become a member.
Today the IDB is owned by 48 member states, of which 26 are borrowing members in Latin America and the Caribbean. Each member country's voting power is based on its subscription to the institution's Ordinary Capital (OC) resources.
To become a regional member, a country needs prior membership to the Organization of the American States. To become a nonregional member, a country needs to be a member of the International Monetary Fund. A second basic requirement in both cases is the subscription of shares of the Ordinary Capital and contribution to the Fund for Special Operations.