Sphingomonas paucimobilis, is a yellow-pigmented, aerobic, non fermentative, gram negative motile bacillus. S. paucimobilis which is widely found in nature and hospital environments rarely cause serious or life threatening infections. In this report, a case of hospital acquired bloodstream infection due to S. paucimobilis in a patient with Down syndrome who was on treatment for presumed pneumonia is presented. A one year-old child patient who was a known case of Down syndrome and had previously experienced cardiac surgery was hospitalized and treated for pneumonia. On the 12th day of hospitalization, blood cultures were taken because of a high body temperature. One of the blood cultures was positive for gram-negative rods. After 48 hour of incubation, the sub-cultures on blood agar medium yielded pure growth of a yellow, non-fermentative, gram-negative, rod-shaped bacterium. The microorganism was positive for oxidase, and esculin hydrolysis, while negative for urea and nitrate reduction, citrate utilisation and motility. The isolate had been identified as S. paucimobilis by using Vitek 2 system. The antibiotic susceptibility test was also performed with the same system and the strain was found to be susceptible to piperacillin-tazobactam and other antibiotics. Treatment with intravenous piperacilin-tazobactam (150 mg/kg/day) was initiated. He responded well to the treatment and was discharged after 10 days. This case is reported to emphasize that S. paucimobilis should be kept in mind as a nosocomial infectious agent in patients with Down syndrome and immunosuppressive patients and the infections should be treated according to the sensitivity test results.