Located in the middle part of Kerala, the District is bound on the East by Madurai District of Tamil Nadu State while on the West by Ernakulam and Kottayam Districts of Kerala. In the South it is the Pathanamthitta District, while on the North it is bound by Trichur and Coimbatore Districts of Kerala and Tamil Nadu States respectively.

It lies between 9 degree 15' and 10 degree 21' of north latitude and 76 degree 37' and 77 degree 25' of east longitudes.

With an area of 5,087 sq.km. Idukki ranks first among the districts in the state in respect of area, forming 13 percent of the total area of the state. It extends by 115km. from south to north and 67km. from east to west.