Psammocambeva exhibits the largest geographical distribution amongst the subgenera of Trichomycterus s.s., with its present northernmost represented by Trichomycterus tete, endemic to the upper Rio de Contas Basin in the Chapada Diamantina Region, north-eastern Brazil. Herein, we describe a new species recently collected in the Chapada Diamantina Region, but in the Rio Paraguaçu Basin, about 100 km north of the area inhabited by T. tete. A molecular phylogeny using one nuclear and two mitochondrial genes (2430 bp) supported the new species as sister to T. tete; both species are distinguished by colour patterns, morphometric data, relative position of dorsal and anal fins and osteological character states. The clade comprising the new species and T. tete, endemic to the semi-arid Caatinga biogeographical province, is supported as sister to a clade comprising species from the Rio Doce and Rio Paraíba do Sul Basins, in the Atlantic Forest biogeographical province. This study corroborated the Chapada Diamantina Region, a well-known mountainous biodiversity centre, as an important centre of endemism for trichomycterid catfishes.