The taxonomically intricate genus of trilobite cockroaches, Parahormetica Brunner von Wattenwyl, 1865, is revised based on a comparative morphological analysis. The goals of this study are to review the nomenclature, propose hypotheses about specific delimitation, and provide diagnoses to allow identification of the taxonomic units in the genus. Based on the revised status of Parahormetica, we transferred Parahormetica hylaeceps Miranda-Ribeiro, 1936, and Parahormetica punctata Saussure, 1873, to the genus Bionoblatta Rehn, 1940. Therefore, the genus includes now four species of giant cockroaches which are predominantly distributed on the Atlantic Forest: Parahormetica bilobata (Saussure, 1864), Parahormetica cicatricosa Saussure, 1869, Parahormetica monticollis (Burmeister, 1838), and Parahormetica museunacional sp. nov. (holotype male deposited in DZUP: Brazil, Paraná). Diagnoses, key, distribution maps, images of living, non-type, and type specimens are made available. Our results make clear that the status and limits among Brachycolini genera pending a full revision.