The Brazilian Northeastern coast includes diverse ecosystems, particularly mangroves, coral and sandstone reefs. Although apparently high, the biodiversity of marine invertebrates from the State of Alagoas is still poorly documented. This study presents 28 new records of opisthobranch molluscs from Alagoas, 11 of which are also new records from the Brazilian Northeastern coast. In addition to comprising an important addition to knowledge about Alagoas reef biodiversity, the new records are useful data for future investigations such as biogeographical studies. Therefore, a list of all opisthobranch species known to date from Alagoas, as well as colour photographs of 32 species is provided.
