This study was carried out to spotlight on the most common parasitic infestation in cultured Sea bass, Dicentrarchus labrax. A total number of 120 Dicentrarchus labrax were collected from two private marine fish farms in Damietta governorate from September 2016 to August 2017. The prevalence, seasonal variation, as well as the histopathological changes in infested
tissues were estimated. the parasitological examination revealed four genera of protozoa including(Trichodina,Epistylis, Amyloodinium and Microsporidia),twogenera of monogenean (Diplectanum and Pseudohaliotrema sp.), one genus of crustacean (Caligus minimus), unidentified digenetic encysted metacercariae , two genera of adult digenetic trematodes
(Timoniella and Bucephalus) and one genus of Nematode (conteracecum) with total prevalence 84.2%. The seasonal prevalence was different from parasite to another. Histopathological examination revealed different pathological changes in the affected tissues as a reaction to parasitic infestation.