Benthic invertebrates were sampled in the Costesti-Stânca reservoir and also downstream and upstream from the riverbed of the Prut River, applying standardized methods, during 2015 – 2022. The sampling stations were Teţcani, Bădragii Noi, Duruitoarea Nouă, Costesti-Stânca dam and Braniste. The low species diversity has been registered in Duruitoarea Nouă and Costesti-Stânca dam. The Branişte and Teţcani stations have the highest species diversity and the high number of rare species, including: Theodoxus transversalis (Pfeiffer, 1828) is a rare mollusk included in The International Union for Conservation of Nature (IUCN) Red List and Palingenia longicauda (Olivier, 1791) is a critically endangered European species has been included in the Appendix II of the Bern Convention, 1998.EPT taxa, the most sensitive groups of benthic invertebrates, have been recorded only in Branişte and Teţcani, downstream and upstream of the Costesti-Stânca reservoir.