We conducted a preliminary survey of the flora at Mt. Mahiru. Mt. Mahiru (1,059 m alt.) is located in the southern part of the Mahiru Mountains, Tohoku district, Japan, and supposedly harbors a wide diversity of northern plants in Japan, although there has been few studies carried out for the flora. On July 30, 2015, we took a route from Akakura-tozan-guchi to the summit of Mt. Mahiru, and collected plants along the trail and on an alpine meadow around the summit. We collected 98 species of vascular plants, including several species that are rarely seen below 1,300 m alt. in Tohoku district, or below 1,700 m alt. in the central or western part of Honshu. Mt. Mahiru is one of the non-volcanic mountains of heavy snowfall with precipitous valleys in the northern Japan, which suggests that it has kept a suitable condition for montane flora without interruptions by volcanic activities. Further studies on the flora and vegetation of the mountain would provide valuable information on a history of the flora of Japan and on a conservation framework of the biodiversity in Japan.