Treatments of species taxonomy for Japanese mammals in “Illustrated Checklist of the Mammals of the World” (CMW) published in 2020 and nine volumes of “Handbook of the Mammals of the World” (HMW) from 2009 to 2019 are compared with those in the second edition of “The Wild Mammals of Japan” (WMJ2) in 2015. Then, the updated taxonomy and current problems of Japanese mammals were discussed. Order Eulipotyphla in CMW and HMW combined orders Soricomorpha and Erinaceomorpha in WMJ2, and Order Cetartiodactyla in CMW joined orders Artiodactyla and Cetacea in HMW and WMJ2; both in reflecting the recent molecular phylogenetic studies. A comparative list of the species names of Japanese mammals between CMW and WMJ2 was made, also with reference to descriptions and literatures in HMW. In CMW, 160 species are found in Japan, and 21 species of them had species names different from WMJ2. Concerning about these species and about species necessary for special consideration in species taxonomy or geographic range, 34 comments were provided for discussion.