The Neyyar sanctuary is spread over the Southeast corner of the Western Ghats, and covers a total area of 128 sq kms. The Neyyar reservoir is easily navigable and extends 9.06 sq. km.

The vegetation varies from tropical wet evergreen to grasslands. The Agasthyarkoodam hill, 1890 metres high, lies in the premises of the sanctuary.

Declared as a sanctuary in 1958, it is the drainage basin for the Neyyar River and its tributaries - Mullayar and Kallar.