The underlying rock is Old Red Sandstone and the terrain generally consists of rocky crags and outcrops interspersed with grassy slopes.

Other habitat types include blanket bog, wet and dry heathland, scree slopes and species-rich grassland.

The dry alpine heath supports heather (Calluna vulgaris), bell heather (Erica cinerea), crowberry (Empetrum nigrum), roseroot (Rhodiola rosea), St. Patrick's-cabbage (Saxifraga spathularis), heath bedstraw (Galium saxatile), dwarf willow (Salix herbacea) and viviparous fescue (Festuca vivipara), together with the ferns Wilson's filmy-fern (Hymenophyllum wilsonii), hard fern (Struthiopteris spicant ), brittle bladder-fern (Cystopteris fragilis), green spleenwort (Asplenium viride), fir clubmoss (Huperzia selago) and the moss Cyclodictyon laetevirens.

Other rare plants were recorded; these included the heath pearlwort (Sagina subulata), the hybrid rush Juncus conglomeratus x J. effusus, and the marsh clubmoss Lycopodiella inundata, found in abundance on one rock ledge on Knockowen.

[4] The Caha Mountains are home to the Kerry slug, otters, badgers, hares, lizards, brown trout and frogs.