Glen Lethnot is in the lower reaches of the Grampian Mountains. The highest hill is The Wirran 2220ft above sea level, the glen is 15 miles long and 5 miles wide approximately, nestled between Glenesk and Glen Ogil.

The West Water is the main river, it is a tributary of the North Esk which flows down Glenesk and reaches the sea at Montrose. It cuts a deep gorge through the sandstone rock in the lower reaches of the glen which can be seen at Pirners Brig.