The recent segregation of 12 genera in the tribe Streblocladieae suggests that the taxonomy of some species belonging to Polysiphonia sensu lato is updated with the transfer and the proposal of new combinations. Accordingly, six new additions to the tribe Streblocladieae on the basis of morphological and molecular analyses are presented as a consequence of this new segregation. These additions include the description of the new species Carradoriella platensis sp. nov., the proposal of the following new combinations Eutrichosiphonia paniculata comb. nov., E. tapinocarpa comb. nov., and the reinstatement of Vertebrata curta, V. decipiens, and V. patersonis. Additionally, our morphological observations identified additional diagnostic features for two genera of the Streblocladieae. Carradoriella has branches with sexual reproductive structures arranged adaxially on branchlets, and the recently described Eutrichosiphonia has rhizoids with multicellular digitate haptera. Our study gives insights in regards to the distribution, the diagnostic features for delimiting genera morphologically, and the molecular evolutionary relationships in the Streblocladieae.