The Amazon is one of the most diverse biomes on Earth, and most of its area is in the territory of Brazil. Even though it harbors most of Earth's diversity, species remain to be described. Therefore, knowing the biodiversity of the Amazon is of utmost importance, and this must be done quickly because the biome is severely under threaten by deforestation. Currently, the Brazilian Amazon has around 340 caddisfly species records, many endemic. To fill gaps in biodiversity knowledge of the Brazilian Amazon, we describe a new species of Oecetis and expand the known distributions of eight species of caddisflies. Oecetis amplicauda sp. nov. can be distinguished from the other species in the O. testacea group by the cylindrical dorsal portion of tergum X, longer than the preanal appendage, and by the inferior appendage with a distinctly enlarged dorsal lobe with stout setae. Four other species of Trichoptera are recorded for the first time for Brazil: Nectopsyche taleola Flint, 1974, Oecetis inflata Flint, 1974, Polyplectropus alienus Bueno-Soria, 1990, and Polyplectropus flintorum Chamorro & Holzenthal, 2010. Three valid species are recorded for the first time in the state of Pará: Marilia paraguassu Rocha & Souza, 2018, Nectopsyche splendida (Navás, 1917), and Polyplectropus rondoniensis Chamorro & Holzenthal, 2010. These results highlight that some caddisfly taxa still lack thorough studies in critical biomes, such as the Amazon, and that imperative actions towards conserving these areas are necessary.