The park is situated in the province of Antsiranana , overthrusting the region of Sambava and that of Andapa stretching over 60 150 ha
Previously, the reserve that comprises the Marojejy mountain and the surrounding spurs changed its status after the passage of the French botanist, the professor Henri Humbert who qualified it as « the most prestigious massif of the whole island both by its imposing aspect, its rich flora and, especially by its character of virgin nature (...) and becomes therefore in 1998 Marojejy National Park .
The granitic mountain is composed of three main zones , that stand and form sharp summits and ridges of quartzite.

Temperate , cold and humid climate with an annual pluviometry superior to 2000 mm : biggest rains in November-December . Low Temperatures in winter on the summits (hardly above 0° C ) .

Humid evergreen forest ( approximately up to 800-900 m of altitude) , mountain humid and dense forest (from approximately 800 to 1500 m of altitude) , mountain sclerophyll dense forest (about 1400 m up to 1800 m of altitude ) and mountain thickets above 1800m of altitude.
The Marojejy is the only great mountain of Madagascar where mountain thicket is intact, if Ankaratra thickets has disappeared , these of Tsaratanàna and Andohahela have been recently damaged by accidental fires .

17 amphibians and 22 reptiles have been counted in the mountain : 5 species of Brookesia and 7 of Chamaeleo among the numerous chameleons found at low altitude .
102 birds species among which Mesitornis unicolor, Neodrepanis hyposantha and Eutriorchis astur (to be checked )
Many lemurs can also be seen in this forest : 23 counted species among them the entirely white fur Propithecus diadema candidus, the known tenrecidae and carnivorous are very few in the park.