A new species of Masteria L. Koch, 1873 from iron ore caves at Caeté and Santa Bárbara, state of Minas Gerais, Brazil, Masteria emboaba sp. nov., is described. It was collected inside caves and in the litter of nearby dry forests. It is the first masteriine species described from southeastern Brazil and the second masteriine species for the country. The new species is the only known Masteria with only two eyes. Additionally, the male of M. emboaba sp. nov. has only two regular, thin spines at the apex of tibia I, lacking the tibial apophysis found in most other Masteria species. The only other described Masteria species that has spines in the place of tibial apophysis is M. aimeae (Alayón, 1995) from Cuba; however, the last species has a longer and sinuous embolus, contrasting the embolus of M. emboaba sp. nov., which is much smaller, less sinuous and transversally placed. The only other described Brazilian species, M. manauara Bertani, Cruz & Oliveira, 2013, has a double tibial apophysis, with both ends tipped by a strong, short spine, and a very long embolus, parallel to the bulb.