Insulodrilus martensi sp. n. is the third species of the genus Insulodrilus reported from Lake Tanganyika (East Africa). A description of the new species is given below and a comparison with its congeners occurring in the same lake is made. From this comparison, the placement of Insulodrilus tanganyikae (Brinkhurst 1970) to the genus Insulodrilus is queried. The creation of a new genus might resolve its ambiguous position, straddling the genera Astacopsidrilus and Insulodrilus.