The genus Proteus has been rarely isolated from cultured fish. In this study, we reported Proteus vulgaris isolated from fish skin lesion of Black-spotted porcupine fish (Diodon hystrix). Identification of f vulgaris was performed by general biological test, including API 20E and API ZYM. The sensitivity of isolated strains to different groups of antibiotics was evaluated using the disc diffusion method. It showed that the isolate is sensitive to ciprofloxacin $(5{mu}g)$, norfloxacin $(10{mu}g)$, enrofloxacin $(5{mu}g)$, cefotaxime $(30{mu}g)$.