This study was carried out in 120 paiches (Arapaima gigas) distributed in four age groups (10 to 30, 31 to 180, 181 to 365 days and >1 year of age) from fish farms in the Peruvian Amazon to determine the prevalence and the affected organs. Eight parasite species ar e repor ted: monogen eans ( Dawestrema cycloancistrium an d D. cycloancistrioides), digeneans (Caballerotrema brasiliense), protozoa (Piscinodinium pillulare, Ichthyophthirius multifiliis and Trichodina sp), cestodes (Schizochoerus liguloides), and nematodes (Nilonema senticosum). The prevalence of parasitism was 0, 66.7, 90.0 and 66.7% for the age groups 10-30, 31-180, 181-365 days and >1 year of age, respectively.