Seafood can present many biological hazards, such as zoonotic parasites. Among these, Ascocotyle (Phagicola) longa trematode is generally found in mullets (Mugil platanus) and is the most common parasite involved in heterophyiosis outbreaks. This research aimed to detect viable metacercariae of Ascocotyle (Phagicola) longa after heating muscle of mullets. The method used was sedimentation followed by microscopy observation. It was found 100% (16/16) of inactivated metacercariae in the analyzed samples. This is the first study involving samples of mullets ready to eat sold directly to consumer. We conclude, consumers must be alerted to the risk of infection by raw mullet eating and proper heating or cooking kills this trematode.