Background: Rat - bite - fever is a rare infectious disease transferred from rats and rodents to human. In Vietnam, as well as Asia, formerly reported pathogen has been Spirillium minus, while Streptobacillus moniliformis has been reported in US, Europe. In June 2016, at the Hospital for Tropical Diseases (HTD), Ho Chi Minh City has recorded a case of septicemia with Streptobacillus rnoniliformis after being bitten by a rat. Objective: To describe a case of rat - bite - fever due to Streptobacillus moniliformis in Vietnam. Result: A male patient, 28 years old, lives in District 4, Ho Chi Minh City, was hospitalized with acute fever after being bitten by a rat for 1 week, accompanied purpura in the arms and legs, muscle pain throughout the body, knee pain, joint shoulder, wrist joints and especially the temporomandibular joint. White blood cells counted 16.000/mm3, Neutrophil' accounted for 74.5 percent, Platelet 113.000/mm3, blood culture result was Streptobacillus moniliformis which is sensitive with Penicillin, Ceftriaxone and Ciprofloxacin. Tile patient was treated with Ceftriaxone 2g/day and 3 days after the fever was decreased, loss of skin lesions, reduced joint pain and was discharged after 14 days of antibiotic treatment. Conclusion: Clinical features of rat - bite - fever easily makes confused with other diseases such as polyarthritis, tetanus ... In addition, related pathogens may be difficult to be found if blood culture is inappropriate. Streptobacillus moniliformis record has not been reported in Vietnam earlier because the agent cannot develop in normal culture or there is a change the geographic location and characteristics of the mouse vector. (28 percent) were urine culture positive, in which there are 50 cases (28 percent) having dipstick neqative and other 332 samples were culture negative.