A total of 360 specimens of Mormyrus rume (Valenciennes 1846) randomly sampled from fish landings along River Ose in southwestern Nigeria were examined for external and internal parasite fauna between April 2005 and March 2007. 39(10.83%) were infected with one or more parasites. The parasites recorded were Monogenea: Dactylogyrus sp, Crustacea: Argulus sp, Nematoda: Anguillicola sp and Digenea: Clinostomum sp. Most of the parasites were recovered from the gills, skin and swim bladder. Larger and older fish were significantly more infected than smaller and younger ones (p<0.05). The difference in prevalence between wet and dry seasons was statistically insignificant (p> 0.05). There was also no significant difference (p>0.05) in prevalence between males and females