North: The boundary starts from Thenmala ridge in the north behind the Divisional Forest Office and it passes towards east to Periyamaruthimalai.
East: The boundary passes between the state boundary of Kerala and Tamil Nadu through Periyamaruthimalai and Karimalai.
South: From Karimalai the boundary runs along the Southern boundary of the Division up to 5 kms and then the boundary between natural forests and plantation till it reaches the Kallada Reservoir up to the dam site.
West: Here the boundary passes along the limits of the Reserve forests between Kallada Dam and Thenmala Divisional forest office.
The Inter state boundary length is 21.8 kms.
The boundary of the sanctuary roughly coincides with the watershed boundary of Kallada reservoir in North, East and South thus making it easy for demarcation and management. The outer boundary of the Sanctuary, eastern boundary, is the interstate boundary between Kerala and Tamil Nadu, which is surveyed and demarcated.
There are three private enclosures namely Rosemala, Kallar estate and part of Rockwood estate situated well inside the sanctuary. These private enclosures lie within the notified boundary.