Plant diets of 2 sympatric species of wood mice in Japan (Apodemus argenteus and A. speciosus) were determined by DNA meta-barcoding analyses of feces using the nucleotide sequences of the chloroplast trnL P6 loop intron region as a molecular marker. The 2 species showed a relatively large degree of niche overlap in plant dietary profiles, feeding mostly on acorn-producing Fagaceae species (assumed to be Quercus crispula). However, A. argenteus was less dependent on Fagaceae species than A. speciosus. Instead, A. argenteus had a wider niche breadth, feeding upon a wider range of plant families such as Betulaceae, Fabaceae, Oleaceae, Pinaceae, Rutaceae, Sapindaceae, Tiliaceae, and Ulmaceae, which were consumed only infrequently by A. speciosus. There was also evidence for species differences in diet across seasons. Oleaceae species (assumed to be Fraxinus mandshurica) were consumed by A. argenteus from June to August, and by A. speciosus from August to October. The results suggested that A. argenteus is a generalist feeder, and A. speciosus a specialist, and the 2 Apodemus species separate their dietary niches not only by the component plant species overall, but also by differences within seasons.