[4] The western end of the range is high P/T metamorphoseed Jurassic accretionary complex[5] as part of the Kamuikotan belt.

[6][7] For the most part, the Hidaka mountains are composed of schists, migmatites, gneisses, and granites.

[9] Mount Apoi is known for endemic alpine plant life, such as Callianthemum miyabeanum (ヒダカソウ, Hidaka-sō).

The topmost zone (1,400–1,600 m) is colonized by Siberian dwarf pine and other alpine flora.

The lowest zone below 500 m is occupied by broad-leafed trees, including Quercus mongolica, Acer pictum subsp.

Notable bird species that transit the Hidaka mountains are Arctic warbler and eyebrowed thrush.