We analyzed 54 specimens of Hoplias aff. malabaricus (Bloch, 1794) collected between March 2010 and March 2011 from the upper Paraná river Neotropical floodplain, Brazil. All hosts were parasitized by at least one species of Monogenea. The parasites species with higher prevalence were Urocleidoides cuiabai Rosim, Mendoza-Franco & Luque, 2011 (96.29 %) and U. malabaricusi Rosim, Mendoza-Franco & Luque, 2011 (92.59%). The community of gill ectoparasites examined showed an aggregated pattern. Urocleidoides cuiabai was the dominant species in the sample (C > 0.25). The parasitic abundance showed significant positive correlation with the standard length of the host for U. malabaricusi and U. eremitus Kritsky, Thatcher & Boeger, 1986. There were significant differences in the abundance values between male and female fish to the species of parasites Urocleidoides brasiliensis Ro...