The Aberdare Mountain Range are part of Kenya's central highlands, running roughly north south between Nairobi and Thomsons Falls. The range rises up to almost 13,000 ft.

The park boundary roughly runs along a 10,000 ft contour. The topography is diverse with deep ravines that give way to gentler valleys separated by steep hills and rocky outcrops. The mountain slopes, especially on the eastern and western flanks, are covered with heavy forest with tree ferns in places giving way to a bamboo zone at higher levels. Above the bamboo trees stretch miles of moorland broken by rocky outcrops and hills, thickets of giant heath and tussok grass. The park is an important water catchment area providing water to the Tana and Athi rivers as well as part of the Central Rift and Northern drainage basins.