The 34-member hemispheric body, meeting in Honduras, unanimously scrapped a 1962 decision that suspended Cuba as Fidel Castro's revolution took the island toward communism and an alliance with the Soviet Union.
U.S. President Barack Obama has taken steps toward a more open relationship with Cuba, lifting restrictions on travel and remittances to Cuba for Cuban-Americans with relatives on the island.
Washington had said Havana should not be allowed to return to the OAS until it embraces democratic principles and makes progress on human rights, and Secretary of State Hillary Clinton came under pressure on Tuesday from Latin American leaders.
In a diplomatic compromise, the group said Cuba's re-entry would be "the result of a process of dialogue begun at the request of the Cuban government and in line with the practices, purposes and principles of the OAS."
That was an apparent reference to the group's stated mission to defend democracy in the Western Hemisphere.
Cuba has repeatedly said it has no interest in returning to the OAS, describing it as an instrument of U.S. policy in Latin America, but Cuba's leftist allies in the region pushed for the suspension to be lifted.
