Both sexes of two new Brazilian phlebotomine sand flies of the genus Nyssomyia Barretto 1962 [ = Lutzomyia (Nyssomyia) sensu Barretto], Nyssomyia delsionatali n. sp. and Nyssomyia urbinattii n. sp., presenting close affinity with Nyssomyia antunesi (Coutinho), are described and illustrated. N. delsionatali n. sp was captured on the edge of a riparian Amazonian forest on the Juruena river in the northwest of Mato Grosso state and N. urbinattii n. sp in a riparian Amazonian forest on the Teles Pires river between Mato Grosso and Pará states. Some measurements of both sexes of N. antunesi and illustration of the male genitalia and the female spermathecae as well as an identification key for males and females of the genus Nyssomyia are provided.