The aim of the present study was to investigate vibriosis in Nile tilapia, Oreochromis niloticus, homologous and heterologous-species pathogenicity to both Nile tilapia and sharptooth catfish, Clarias gariepinus, the histopathological lesions in infected fish, and the antibiogram characters of the strains isolated. Twenty four isolates of suspected Listonella anguillarum were recovered from 16 out of 150 Nile tilapia collected from River Nile and El-Ibrahemia canal at Assiut governorate. Suspected isolates were identified as L. anguillarum according to the cell morphology, gram stain, colony morphology, biochemical characters, and enzyme activities. The pathogenicity of      L. anguillarum to Nile tilapia and sharptooth catfish were investigated by an experimental challenge. Challenged fishes showed typical signs of vibriosis including general speticaemia and ascites, and accumulation of bloody exudates in the intestine. The average total mortality rates were 73.3 and 93.3% in Nile tilapia and sharptooth catfish, respectively, by the end of the challenge. The histopathological changes associated with vibriosis were mainly in the kidneys, livers, and spleens of challenged fish. The antibiotic sensitivity test for L. anguillarum revealed their high sensitivity to ampicillin and oxytetracycline.