Geologically, the Kitakami Mountains are Paleozoic and Mesozoic formations, divided into northern and southern groups.

the southern area has oldest previous Silurian foundation, which was once a shallow sea on the continental margin where the water temperature was high enough for coral growth from the Silurian to the Devonian periods; this region, later collided with the northern Kitakami mountainous area in the early Cretaceous period, and the whole was penetrated by the granite in various places.

The uplift of the Ōu mountain range began in late Miocene and the Kitakami Basin was born.

In addition, as a result the glacier effects of the last glacial period, the current gentle topography was created.

Mount Hayachine, near the center of the range, is the highest peak at 1,917 metres (6,289 ft), and supports endemic alpine vegetation.