Throughout East Asia, Europe, and North America, mammalian orthoreovirus (MRV), for which bats have been proposed to be natural reservoirs, has been detected in a variety of domestic and wild mammals, as well as in humans. Here, we isolated a novel MRV strain (designated as Kj22-33) from a fecal sample fromVespertilio sinensisbats in Japan. Strain Kj22-33 has a 10-segmented genome with a total length of 23,580 base pairs. Phylogenetic analysis indicated that Kj22-33 is a serotype 2 strain, the segmented genome of which has undergone reassortment with that of other MRV strains.