Reuters reported in August that Luiz Inacio Lula da Silva, elected as Brazil's president at the end of October, would seek a partnership with the two other leading rainforest nations to pressure the rich world to finance forest conservation.
The rapid destruction of rainforests, which through their dense vegetation serve as carbon sinks, releases planet-warming carbon dioxide, imperiling global climate targets.
"South-to-south cooperation - Brazil, Indonesia, DRC - is very natural," the Democratic Republic of Congo's Environment Minister Eve Bazaiba said prior to the signing.
In the agreement, the alliance said that countries should be paid for reducing deforestation and maintaining forests as carbon sinks.
Talks on the alliance to protect rainforest until now had foundered due to "institutional difficulties," Teixeira said.