A four-year survey for Notonectidae (Insecta: Hemiptera: Heteroptera: Nepomorpha) was conducted in eleven conservation units and adjacent areas distributed over six states in northeastern Brazil. Nearly 1400 specimens of the following 18 species, four genera, and two subfamilies have been collected: Buenoa amnigenus (White, 1879), B. femoralis (Fieber, 1851), B. fuscipennis (Berg, 1879), B. koina Nieser & Pelli, 1994, B. konta Nieser & Pelli, 1994, B. mutabilis Truxal, 1953, B. pallipes (Fabricius, 1803), B. platycnemis (Fieber, 1851), B. pseudomutabilis Barbosa, Ribeiro & Nessimian, 2010, B. salutis Kirkaldy, 1904, B. tarsalis Truxal, 1953, B. unguis Truxal, 1953 (Anisopinae); Enitharoides brasiliensis (Spinola, 1837), E. tricomerus Barbosa, Ribeiro & Nessimian, 2017, Martarega bentoi Truxal, 1949, M. brasiliensis Truxal, 1949, M. membranacea White, 1879, and Notonecta disturbata Hungerford, 1926 (Notonectinae). Altogether, they represent 30 new records from the states of Alagoas, Bahia, Ceará, Pernambuco, PiauĂ, and Sergipe, and seven new records from northeastern Brazil, increasing the number of species recorded from the region from 11 to 18. A key to these species is provided, as well as illustrations, diagnoses, taxonomic notes, and a summary of their known geographic distributions.