Helicometrina nimia (Opecoelidae) is a digenean with wide distribution. Fish families most commonly used as hosts for H. nimia are Serranidae, Pomodasydae, Scorpaenidae and Clinidae. In the present study, a new host and a new host locality are presented for the species. A description of the studied specimens, besides comments concerning its taxonomic status and biometrically compared tables of H. nimia reports are given. The taxonomic status of members of Helicometrina has been questionable. The greatest controversy for the genus seems to be related to the validity of diagnostic features, especially in regard to the number of testes. In the present study, all studied specimens presented a permanent and steady number of testes (n=9) and therefore its use as a diagnostic character is supported by the present authors. Epinephelus marginatus is considered a new host for Helicometrina nimia, and São Paulo state, southeastern Brazil, a new locality for the species.