It covers 315,000 hectares (780,000 acres) of the Serra do Mar mountain range, and is one of the largest remaining areas of continuous Atlantic Forest.

The State Park stretches from the border of Rio de Janeiro to Itariri in the southern part of São Paulo.

The Serra do Mar State Park was created in 1977 when the BR-101 coastal highway was built, and expanded in 2010.

It connects the Serra do Mar forests of Rio de Janeiro to the Vale do Ribeira and Paraná.

The park protects water sources that supply part of the São Paulo metropolitan region, Baixada Santista, Litoral Norte, and the Paraíba Valley.