There is no consensus as to the level of intraspecific morphological plasticity in calcareous sponges, and so many species described in the nineteenth century were lumped into a few supposedly very polymorphic species during the 20th century. Leucetta floridana was originally described from Florida, but was subsequently considered as a junior synonym of the Pacific species Leucetta microraphis, in spite of the presence, in L. floridana only, of two size classes of tetractine spicules. We have compared, through DNA sequencing (ribosomal internal transcribed spacers, ITS1 and ITS2) and detailed morphological analyses, samples of Leucetta cf. floridana from the Atlantic (three sites in the Caribbean, and five along the Brazilian coast), with L. microraphis from the Pacific (Australia and New Caledonia). Not only did the genetic and morphological analyses confirm the taxonomic validity of L. floridana, but they also detected the presence of a new species of Leucetta, morphologically similar to and living in sympatry with L. floridana in the Brazilian coast.