Tawarau Forest is the best remaining North Island example of a virgin forest growing in a karst (limestone) landscape. It is dominated by tawa and other trees such as hinau, kamahi, and rewarewa and emerging podocarps such as rimu and miro. Tarawau Forest is known for its 'cool climate' vegetation, with mountain cabbage trees growing at an unusually low altitude.

It is home to a variety of New Zealand birds including falcon, grey warbler, tomtit, kereru, riflemen, bellbird, whitehead, and in summer, long-tailed cuckoo. Tawarau Forest is also home to long-tailed bats as well as having an exceptional diversity of land snails with 82 different species recorded.

There are many caves in the forest and probably some unexplored ones.