Culex (Melanoconion) sacchettae Sirivanakarn and Jakob, 1981 from southern Brazil is redescribed and compared to the closely related species, Cx. vomerifer Komp, 1932 and Cx. portesi Senevet and Abonnenc, 1941. Female adults, male adults, male genitalia, pupae and larvae are described and illustrated. Data about known distribution, bionomics and epidemiological importance are presented.