A middle Permian (Wordian) brachiopod fauna, consisting of 19 species in 18 genera, is described from the lower part of the Kamiyasse Formation in Matsukawa, South Kitakami Belt, northeastern Japan. The Matsukawa fauna is a mixed Boreal—Tethyan brachiopod fauna that shows strong affinities with the middle Permian (Wordian—Capitanian) brachiopod faunas of central Japan (Hida Gaien Belt), eastern Russia (South Primorye), northeastern China (Heilongjiang), northern China (Inner Mongolia) and northwestern China (Xinjiang). The palaeobiogeographical data suggest that Proto-Japan, including South Kitakami, was part of a continental shelf along the northern and eastern margins of North China, located in the mid-latitudes of the Northern Hemisphere during the middle Permian (Wordian).