Microbial infections in tilapia aquacultures cause severe economic losses in Egypt. They appear in summer with other stress factors such as low oxygen and high ammonia levels in aquaculture. Streptococcosis lead to severe losses in tilapia farming, especially in third countries. Microbiological and histopathological examinations are very important diagnostic tools in distinguishing fish microbial infections. This study aimed to isolate, identify, and characterize the most common bacterial fish pathogen recovered from Nile tilapia private farm around El Salam Canal, at Ismailia governorate. In addition to detection the main histopathological lesions were done. The highest rate of bacterial isolation was Streptococcus agalactiae with 29.16% from all samples. Grossly the infected fish showed hemorrhagic septicemia, and exophthalmia. Histopathological examination revealed severe hyperemia of gill filaments and gill arch, chronic enteritis, hydropic degeneration of the liver, edema and hemosiderosis of the spleen, necrosis of muscle and hemorrhage and myocardiolysis of heart.