Comamonas testosteroni is a Gram- negative, aerobic, motile, non-spore-forming bacillus. It has not been recognized as a component of the endogenous human microflora. Due to its ability to survive in liquid environments, it can survive for a long time in a hospital environment and cause opportunistic infections. Although rare, C. testosteroni has been reported as a cause of cellulitis, peritonitis, endocarditis, meningitis, endophthalmitis, tenosynovitis, pneumonia and bacteremia. Here, we present a case of a 4-yearold girl who was operated on for persistent cloaca with C. testosteroni isolated in her urine culture. Identification studies were performed by MALDI-TOF MS (bioMerieux, France) mass spectrophotometer method. Antibiotic susceptibility tests were performed with the automatic device VITEK-2 Compact (bioMérieux, France). Microorganism was found susceptible to ceftazidime and ciprofloxacin; intermediate susceptible to meropenem and piperacillin / tazobactam and resistant to gentamicin, amikacin, imipenem and trimethoprim-sulfamethoxazole. With this case report, C. testosteroni was reported as the first cause of urinary tract infection in our country and the third in the world.