The reserve contains a diverse array of tall open forests, open forests, woodland, closed heath and closed herbfield. Most of the reserve supports Subalpine Dry Shrub Open Forests and Woodlands, a vegetation type that was once widespread in the region but is now confined to remnant stands. Three species of significance have been found within the reserve, including the endangered Kydra westringia.
Coolumbooka Nature Reserve provides valuable habitat for local fauna, with a total of 127 species having been recorded to date including three threatened species. Potential habitat also occurs for a large number of other threatened species but further survey work is recommended to ascertain their presence or absence.