The genus Dicellophilus Cook, 1896, is a peculiar genus from the point of view of distribution. Dicellophilus is distributed in three limited areas that are well separated from one another: central Europe (D. carniolensis), Honshu (D. pulcher), and the southwestern part of the USA (D. anomalus and D. limatus). In the present study, in a field survey conducted throughout Japan, specimens belonging to the genus Dicellophilus were collected from Tohoku to the Kansai region, Honshu. Morphological analysis, molecular phylogenetic analysis, and genetic distance among Dicellophilus in Japan and D. carniolensis revealed that specimens from Sendai-shi, Miyagi Pref., could be assigned to an undescribed species. This previously unrecognized species is herein described as D. praetermissus sp. nov. The new species can be distinguished from D. carniolensis and D. limatus by the number of pairs of legs (43 pairs in D. carniolensis and 45 in D. limatus, but 41 in D. praetermissus sp. nov.), from D. anomalus by the lack of a pair of setae on the posteromedian part of the clypeus and variable crenulation on the internal margin of the forcipular tarsungulum, and from D. pulcher based on the following combination of characteristics: both ends of the transverse suture not evidently convex forward; long rather than wide trochanteroprefemur; wide rather than long metasternite.