A plant morphologically intermediate between Viola rostrata Pursh var. japonica (W. Becker et H. Boissieu) Ohwi and V. violacea Makino var. makinoi (H. Boissieu) Hiyama ex F. Maek. was found in Iwate Prefecture, Tohoku District, northern Japan. Molecular analysis based on sequences of internal transcribed spacer regions of nuclear ribosomal DNA and trnL-trnF intergenic region of chloroplast DNA indicated that the intermediate plant was a hybrid between those two species and that the maternal parent was V. rostrata var. japonica . This is the first report of a naturally occurring intersubsectional hybrid of subsect. Rostratae Kupffer and subsect. Adnatae W. Becker.