Abstract Snails of the genus Stramonita are commonly found in the rocky intertidal habitat of the western Atlantic Ocean coast. They belong to a monophyletic taxon that occurs along the tropical and warm-temperate Atlantic and eastern Pacific rocky shores. This genus comprises different valid species and members of the S. haemastoma complex. In the present study, samples of Stramonita were collected from three different regions of southeastern Brazil. Partial sequences of two mitochondrial genes, COI and 16S rRNA, were used to compare nucleotides sequences between Stramonita specimens. Levels of nucleotide divergence greater than 2% across the three sampled regions were used for differentiation at the species level. One of the identified species was S. brasiliensis, which has recently been described by molecular analysis; the other species may represent S. haemastoma, not yet described in the southeastern Brazilian coast.