In the present study, we describe a new species belonging to the genus Chalinula from Ilha Grande Bay, Rio de Janeiro state, off Southeast Brazil. Chalinula tamoiensis sp. nov. is thinly to thickly encrusting, purple or pink coloured in life, with oscules raised in volcano shaped projections or more commonly flush with the surface, in thinly encrusting specimens. Skeleton typically anisotropic, with variable amounts of spongin and oxeas ranging from 59 to 90 µm long. Maximum likelihood analyses of large ribosomal subunit DNA (28S rRNA) recovered Chalinula polyphyletic. Chalinula tamoiensis sp. nov. clustered with a subset of species from other ocean basins and was distantly related to Chalinula molitba, from the Tropical Western Atlantic and Chalinula nematifera, from the Central Western Pacific, with which it shares a series of traits. A summary of morphological characters of all species belonging to the genus and new sequences of the larger ribosomal subunit DNA are also provided.