A new species of Congosorex is described. The new species occurs in Tanzania and is larger in external characteristics than the other two known species in the genus, with the longer tail being especially distinctive. The skull of the new species is wider, on average, than other Congosorex, but intermediate in greatest length. Previously undocumented characteristics that differentiate Congosorex from Myosorex are described. The presence of Congosorex in the Eastern Arc Mountains supports the theory that these mountains are refuges of ancient lineages of organisms with ties to the Guineo-Congolian region of Africa and that there was once a continuous swath of forest connecting these two areas.