The internal reproductive systems of six species of genus Nephrotoma Meigen, 1803 are described and illustrated. The paired spermathecae are discovered in N. bifusca, representing the first record of two spermathecae in the genus Nephrotoma and even in the family Tipulidae, where three spermathecae were previously considered constant. Morphological differences in internal reproductive organs among these species are documented. Additionally, the taxonomic potential of internal reproductive structures is analyzed and discussed.