Perumytilus purpuratus is a mussel commonly found on the entire Chilean coastline. The knowledge of pathogens and parasites of this mollusc, as well as for many other species, inhabiting the Chilean coast remains largely unknown. This study aims to survey parasites and pathogens in P. purpuratus from San Jorge Bay, Antofagasta, Chile. From September to October 2009, 160 specimens of this bivalve were collected. Ciliates, virus-like, rickettsia-like organisms (RLO) and digeneans were recorded. The most prevalent parasites were metacercariae of digeneans in gonads (50.83%), gill ciliates (37.5%), and digestive gland viruses-like (37.5%). Only the prevalence of digeneans increased with host size, but any relationship between these variables was found in the other pathogens.