With an elevation of 1,274 m (4,180 ft) on the southern slopes of Mount Yatsugatake, Kai-Ōizumi Station is the third highest station on the JR East rail network.

The station consists of two ground-level opposed side platforms, connected by a level crossing.

The station has a Midori no Madoguchi staffed ticket office.

Kai-Ōizumi Station was opened on 27 July 1933 by the Japanese Government Railways.

With the privatization of Japanese National Railways (JNR) on 1 April 1987, the station came under the control of JR East.