Based on specimens collected from eulittoral zone in rocky shores of northeast of Rio de Janeiro (Brazil) on 2017, two new tanaidaceans species from two different suborders are described: Apseudomorpha brasiliensis sp. nov. (Apseudomorpha, Metapseudidae) and Pseudozeuxo fischeri sp. nov. (Tanaidomorpha, Pseudozeuxidae). Diagnostic characters of Apseudomorpha brasiliensis are mandible palp article-2 and article-3 with six and nine finely penicillate setae on inner margin, respectively; pereopod-1 carpus and propodus with two and four ventral spines, respectively; pleonites 2 and 5 with pleura having long distal seta; uropod exopod shorter than endopod articles 1–2 combined, endopod four-articled. Pseudozeuxo fischeri is characterized by pereopods 1–3 coxa with long seta about half as long as basis; pereopods 2–3 carpus with ventrodistal seta; propodus with two ventral setae; pereopods 4–6 propodus with two ventral spines and one seta; uropod endopod two- and exopod one-articled. This is the first record of the family Pseudozeuxidae and the metapseudid subfamily Metapseudinae from the Southwestern Atlantic (Brazil). Remarks on their associations with macroalgae and identification keys to world species of Apseudomorpha and Pseudozeuxo are provided.