A 3.4 year-old rhesus macaque weighing 4.5 kg, was suffering from anorexia, acute mucous and bloody diarrhea. On physical examination, the monkey showed a loss of activity, hunched posture, abdominal pain, dehydration, mild gingivitis and unclean anus with discharge. Whole blood was collected for the examination of electrolytes, hematology and serum chemistry; fresh stool was also collected for bacterial culture. Blood profiles showed leukocytosis (14.5 K/µL) and neutrophilia (11.0 K/µL) on complete blood cell count and imbalanced electrolytes associated with diarrhea. As a result of bacterial culture, Shigella flexneri was identified through Mac/SS, IMVIC test, TCBS and VITEK II. Based on these results, this monkey was diagnosed as having acute enteritis caused by Shigella flexneri. Treatment was performed with enrofloxacin prior to the isolation of Shigella flexneri to prevent the transmission of disease. Fortunately, mucus and bloody diarrhea did not persist and general conditions fully recovered. Our results show that the use of enrofloxacin is effective in controlling Shigella flexneri infection in newly acquired rhesus monkeys.