Vibriosis is one of the most serious diseases affecting fish farming industry worldwide . The study aimed to identify Vibrios spp. causing infections and mortalities in farmed Nile tilapia, Oreochromis niloticus. Haemorrhages , exophthalmia, fin rot, erosions and ulcerations were commonly observed in moribund fish. Poor water quality parameters, management practices and biosecurity measures were reported in all investigated farms . Thirty eight Vibrio isolates were obtained and identified from investigated specimens using phenotypic and molecular identification methods. Vibrio alginolyticus was the most prevalent isolate (37%), followed by Vibrio anguillarum (24%) , Vibrio vulnificus (18%) , Vibrio paraheamolyticus (13%) and Vibrio cholera (8% ). Different virulence genes were detected in all tested isolates. Vibrios exhibited resistance against some antibiotics. The highest resistance was noticed against amoxicillin and tetracycline. Pathogenicity of vibrio isolates were confirmed by experimental infection in O. niloticus . Challenged fish showed signs of septicemia and variable mortality with numerous histopathological alterations. Our findings highlight the risk of vibrios to farmed O. niloticus , point to the need of effective control and biosecurity measures to protect fish health.