Infectious endogenous endophthalmitis can occur by entrance of a pathogenic microorganism into the eye from various primary infection sites other than the eye. Although relatively rare, it results in visual loss frequently in spite of early diagnosis and treatment. It occurs in the process of systemic infection and its underlying conditions are diabetes, advanced liver disease, and immune suppressive state or drug abuse. We report a case of a 51-year old man with proliferative diabetic retinopathy and endogenous endophthalmitis caused by S. aureus from a skin infection. The ocular symptoms improved after systemic and intravitreal antibiotic therapy but visual loss could not be prevented. In conjunction with this case, we review the available literatures and stress the seriousness of this disease when concurrent in diabetic patients.