The Blackwater River, a tributary of the upper Cheat River of the Monongahela River, hosts a modest fish fauna. This relatively low diversity of fish species is partly explained by its drainage history. The Blackwater was once part of the prehistoric, northeasterly flowing St. Lawrence River. During the Pleistocene Epoch, the fauna was significantly affected by glacial advance and by proglacial lakes and their associated overflows. After the last glacial retreat, overflow channels, deposits, and scouring altered drainage courses and connected some of the tributaries of the ancient Teays and Pittsburgh drainages. These major alterations allowed the invasion of fishes from North America's more species-rich southern waters. Here we review fish distributions based on 67 surveys at 34 sites within the Blackwater River drainage, and discuss the origin and status of 37 species. Within the Blackwater River watershed, 30 species (20 native, 10 introduced) have been reported from upstream of Blackwater Falls, whereas 29 (26 native, 3 introduced) have been documented below the Falls. Acid mine drainage, historic lumbering, and human encroachment have impacted the Blackwater's ichthyofauna. The fishes that have been most affected are Salvelinus fontinalis (Brook Trout), Clinostomus elongatus (Redside Dace), Nocomis micropogon (River Chub), Hypentelium nigricans (Northern Hog Sucker), Etheostoma flabellare (Fantail Darter), and Percina maculata (Blackside Darter). The first two species incurred range reductions, whereas the latter four were probably extirpated. In the 1990s, acid remediation dramatically improved the water quality of the river below Davis. Recent surveys in the lower drainage revealed 15 fishes where none had been observed since at least the 1940s; seven of these (Cyprinella spiloptera [Spotfin Shiner], Luxilus chrysocephalus [Striped Shiner], Notropis photogenis [Silver Shiner], N. rubellus [Rosyface Shiner]; Micropterus dolomieu [Smallmouth Bass]; and Etheostoma camurum [Bluebreast Darter] and E. variatum [Variegate Darter]) represent additions to the faunal list of the Blackwater River.