In order to inventory the metazoan endoparasites of Serrasalmus marginatus, 91 specimens were examined. They were captured in the Negro River in Pantanal wetland, State of Mato Grosso do Sul, Central-Western Brazil, from October 2007 to August 2008. Parasites of six taxa were recovered: Procamallanus (Spirocamallanus) inopinatus, Contracaecum sp. (Nematoda), metacercarial type Diplostomulum (Digenea), Brevimulticaecum sp. (Nematoda) and Sebekia oxycephala, Subtriquetra sp. 1 and Subtriquetra sp. 2 (Pentastomida). The latter five species are reported for the first time in S. marginatus.