BACKGROUND: European chub (Squalius cephalus) is a member of Cyprinidae family and is classified as fresh water fishes which live in a group in roaring rivers. Siahrood runs from the south east to the Caspian Sea. OBJECTIVES: The main objective of this study was determination and identification of parasites of European chub in the Siahrood river. METHODS: In the current study, a total number of 96 fishes with average weight of 42 ± 3 gr and average length of 15 ± 1 cm were collected during winter, spring, summer and autumn 2015. The collected fishes were transported to parasitology lab with oxygenated plastic bags and were kept in aquarium till examination. Sample collection was conducted from skin, gills, fins and eyes and prepared wet mount was studied with optical microscope. Samples which are positive for presence of parasite were fixed and identified at the level of genus or species by biometric characterization and identification keys. RESULTS: In the present study, 6 species of endo parasites and ecto parasites were detected from different organs of Siahrood’s European chubs that included: 2 protozoan species from gills, Ichthyophthirius multifiliis with the highest positive samples in summer; Trichodina sp. with the highest positive samples in spring; 1 Myxozoa species from the intestine, Myxobolus  muelleri with the highest positive samples in winter; 3 Monogenea species, Dactylogyrus vistulae and Diplozoon paradoxum from the gills with highest positive samples at autumn and summer respectively; Gyrodactylus mutabilitas from the gills and the skin with the highest positive samples in summer. CONCLUSIONS: It seems the major factors affecting the variable presence of parasites in different seasons are ecological and environmental variation of the river in different seasons and the effects of these changes on fishes physiology and parasites life cycle.