Freshwater fish biogeography can provide insight into past connectivity of river systems. Here we report the first discovery of the large-bodied cyprinid Acapoeta tanganicae (Boulenger, 1900) inside the Lake Rukwa catchment. Previously this species was thought to be endemic to Lake Tanganyika and immediately proximate sections of connected rivers. This shared distribution supports a scenario of direct connectivity of the two catchments during Holocene high stands of Lake Rukwa.