The new genus Yanomamius n. gen. from Brazilian and Venezuelan Amazon is described, with three new species from Brazil: Y. franciscoi n. sp. (type species), Y. raonii n. sp., and Y. neblina n. sp. The enigmatic Venezuelan species described as Holothele waikoshiemi Bertani & Araújo, 2006 and presently included in Guyruita Guadanucci et al. (2007) is transferred to the new genus, making the new combination Y. waikoshiemi (Bertani & Araújo, 2006) n. comb. Yanomamius n. gen. is closely related with the schismatotheline genera Schismatothele Karsch, 1879 and Euthycaelus Simon, 1889 sharing as probable synapomorphies a group of short spines on the retrolateral distal tibia of male palp and the shape of bulb. They differ by the position of the spines in a compact group instead of in rows and by a tapering embolus. Females differ from Schismatothele and Euthycaelus by the spermathecae weakly sclerotized. A series of recent phylogenies based on molecular data suggested a close relationship between schimatothelines and psalmopoeines. The male tibia I of Yanomamius n. gen. species have a series of ridges or a single protuberance behind the tibial apophyses that resemble those of psalmopoeines and strengthen the idea of close relationship of the two subfamilies.