Pentamera paraibanensissp. n. is described from more than 3000 specimens as a new species of Phyllophoridae from northeast Brazil, in the tropical southwestern Atlantic. It is distinguished from its congeners by the shape of the calcareous ring with moderate posterior processes, and by the tables in the body wall with a usually quadrilocular disc and a low, toothed spire composed of two pillars. The body is brown, with the tube feet in double rows per ambulacrum, and tentacles more lightly colored. The species was found inside rodoliths in large numbers. This paper contains a morphological description of the specimens, and an account of their habitat characteristics.