Bacteria of the genus Vibrio, which is included in the family Vibrionaceae are commonly found in coastal and estuarine waters. Many Vibrio species can cause diseases in marine fish, crustacean and bivalve species. Moreover, many of them can infect humans after a contact with these animals or consumption of these animals and cause zoonoses. Vibrio harveyi, which was first isolated as a causative agent of a disease problem in a shark species in 1982, was deter-mined to cause diseases and mass mortalities especially in marine invertebrates and in a variety of fish species including aquacultured species such as gilthead sea bream, sea bass and salmo-nid fishes. Deep skin lesions and ulcers, gastroenteric disorders and eye lesions were observed in fish infected with V. harveyi. Primer isolation of this organism can be made on general me-dia such as Tryptic Soy Agar (TSA; supplemented with 2% NaCl) and Thiosulphate-Citrate-Bile salts-Sucrose (TCBS) (semi selective medium for Vibrio species). Besides, Vibrio harveyi Agar (VHA), a media which is developed specially for this species can be used for isolation and species identification. Chloramphenicol, ciprofloxacin and oxytetracycline are recom-mended for the control of disease by various researchers. The aim of this review is to present data to the fish farmers and fish health specialists on the etiology, epizootiology, pathogenicity, clinical symptoms and the pathology, diagnosis, protection and control of Vibrio harveyi and some studies on V. harveyi which is a worldwide distributed bacterium and the causative agent of diseases and mass mortalities in marine animals.