Ornamental fish are considered a large business opportunity potential for people cultivating freshwater fish due to their high prices where fish farmer can open profitable business. Consequently, it is essential to continuously sustain health of fish. The study is designed to detect the external parasite monogenea sp. and evaluate the prevalence of infestation in five ornamental fish species goldfish [Carassius auratus], guppy [Poecilia reticulata] koi carp [Cyprinus carpio], glofish tetra [Gymnocorymbus ternetzi] and molly [Poecilia latipinna]. Fifty samples from every fish species were taken, totaling 250 collected during the period from September 2025 to February 2026. Microscopical examination results revealed a total infestation rate with Dactylogyrus sp. was 10.8 % with no significant differences at p = 0.827 while the total infestation rate with Gyrodactylus sp. recorded 12.4%. with no significant differences at p = 0.4297. The results also showed the sites of infestation in Goldfish in the gills, skin and fins where the number of Dactylogyrus sp. was detected only on gills 28 while the site of infestation in Gyrodactylus sp. was higher on fins 18 then skin 15 and the lowest on gills 2. The study concluded that all five fish species examined were exposed to a similar level of infestation indicating that poor management increases infestation rate with Gyrodactylus and Dactylogyrus and considered a major problem in ornamental fishkeeping in Mosul-Iraq.