Colletes jankowskyi Radoszkowski is recorded from Japan for the first time. It is similar to C. babai Hirashima & Tadauchi and C. floralis Eversmann of the Japanese congeners, but is separated from these allied species by the combination of following characters: malar space short, less than one-half of basal width of mandible; mesoscutum with whitish hairs mixed with darker ones; first metasomal tergum with dense punctures; and hair zone on disc of seventh metasomal sternum narrow in central area. DNA barcodes are also useful for discrimination among these three species. The habitat of Japanese C. jankowskyi may be limited to semi-natural grassland. Adults appeared from mid-August to mid-September. The number of individuals is richest from late August to early September, although the species had been collected earlier in the season on the Asian mainland. Most specimens were collected on flowers of Lespedeza cyrtobotrya Miq. (Fabaceae). In Japan, C. jankowskyi is suggested as a relict species judging from the distribution and habitat information.