Along with Mount Mabla, the Forêt du Day National Park is one of Djibouti's two remnant areas of closed−protected forests.

It has four dominant tree species: Juniperus procera, Olea europaea subsp.

The most valuable part of national park is 900 hectares (2,223 acres) large stand of East African junipers Juniperus procera which grows in the heights above 950 m. Junipers here reach height of 20 m, but many trees have died off in recent decades, while the boxwood B. hildebrandtii is expanding in their stead.

Notable animals found here include the Djibouti spurfowl (Pternistis ochropectus), a population of green-winged pytilia that may actually be a distinct species or subspecies (Pytilia (melba) flavicaudata), as well as the mysterious and undescribed Tôha sunbird—Djibouti sunbird (Chalcomitra sp.

All of these birds do not occur outside of and are endemic to Djibouti, and except for the Francolin they have only ever been found within Day Forest.