[3][4] The municipality contains part of the 230,296 hectares (569,070 acres) of the Caminhos Ecológicos da Boa Esperança Environmental Protection Area, created in 2003.

Francisco Romeo, administrator of the Captaincy of São Jorge dos Ilhéus founded a small settlement in Cairu based on its mild climate.

The settlers displaced the Aimoré and the settlement, known as the Vila de Nossa Senhora do Rosário do Cairú, was established in 1608.

The Franciscans arrived in 1654 to build the Convent and Church of Saint Anthony on another high point in the settlement.

[6][4] Cairu is home to numerous colonial-period historic structures, some designated as Brazilian state or national monuments.