Ornamental fish culturing has been altered into one of the most vital and profitable industries in numerous countries all over the world. The cultivation and propagation of ornamental fish have been increasing in the last few years in Iran. Qom is one of the provinces where this industry has expanded significantly. The purpose of this study was to investigate the parasitic infections in 14 ornamental fish farms, where diseases and death had been reported in different fish species. This research was carried out for seven months from November 2021 to May 2022 on 15 different species of referred ornamental fish. Ornamental fish species including Gymnocorymbus ternetzi, Poecilia reticulata, Poecilia sphenops, Carassius auratus, Hyphessobrycon eques, Pterophyllum scalare, Danio rerio, Betta splendens, Puntius tetrazona, Hemigrammus ocellifer, Ancistrus sp., Heros severus, Andinoacara rivulatus, Cyprinus rubrofuscus, and Melanotaenia praecox were sampled and examined for internal and external parasitic infestations by light microscopy. In the results, external parasites including Trichodina sp., Gyrodactylus sp, Lernaea sp, Ichthyobodo sp., Tetrahymena sp., Oodinium sp., Dactylogyrus sp., and Ichthyophthirius multifiliis and internal parasites including Capillaria sp., and Hexamita sp. were detected. The highest prevalence of parasites was related to Capillaria sp. (17.69%) and the lowest prevalence was related to Lernaea sp. and Ichthyobodo sp. (0.77%). It was concluded that these findings can help to develop a program for the prevention and treatment of parasitic diseases in freshwater aquarium fish.