Naturally Kohila Municipality belongs to the area of the North-Estonian plateau. The landscape is mostly even with some higher sloped areas, the differences of heights of which rarely exceed 10 metres. Absolute heights of land surface remain within 55-75 m.

The surface soil layer has a low thickness and in some places flagstone directly reaches the land surface. There are wide karst areas in the municipality, and many of them are naturally highly visible (Aandu, Hageri, etc.). Due to the nature of the karst areas a larger part of underground water of the municipality territory is poorly protected. Rabivere marsh serves as the main water body of the western part of the municipality. One part of the marsh is used for industrial production of peat.

Keila river runs through the north-western and south-eastern parts of the municipality, and its riverscape has a high historical and cultural value. The municipality itself serves as a unique watershed – from here the Maidla and Vasalemma rivers of the basin of Gulf of Finland start, and the Angerja brook, Pirita's tributary belonging to the Tallinn pumping station runs through the eastern part of the municipality. Kasari river (originally called Teenuse) belonging to the basin of Väinameri starts in the southeastern part of the municipality.

Almost 44% of the municipality territory is covered with woods, and the most widespread types of trees are fir and pine. Irreparable damage to the quality of the woods was caused by the infamous August storm of 1967. It is also worth to mention our rare alvar forests.