Few studies have been done to evaluate the monogenean microhabitat preference. This study evaluated the monogenean distribution among different gill arches of Nile tilapia Oreochromis niloticus and seasonality. A total of 89 fish were captured in a pond located in Chapecó, Santa Catarina, for parasitological analysis. After fish euthanasia, the gill arches were removed, separated from the most external to the most internal and named as I, II, III and IV. Transparency, pH, oxygen, temperature, alkalinity, conductivity, ammonia, iron, orthophosphate, sulfide, nitrite and nitrate of water pond were measured. In spring 2008 the mean abundances of the monogeneans (Scutogyrus longicornis, Cychlidogyrus sclerosus, C. thurstonae and C. tilapiae) in the arches I, II, III and IV were, respectively, 11.45, 14.45, 13.8, 13.15, in summer 2008 theywere 13.12, 12.25, 14.94, 21.53, in summer 2009 they ...