We present a case of urosepsis by Citrobacter koseri in an 87-year-old woman affected by hypertension, myocardial ischemia and chronic renal failure. The patient had been previously hospitalized for pneumonia and pyelonephritis caused by K. pneumoniae. The isolation of Citrobacter, although uncommon, is clinically relevant in the majority of cases. We analyzed the risk factors, the clinical features, the resistance profile and the treatment of this mostly nosocomial infection, comparing our case with other cases of urosepsis due to Citrobacter found in literature from 1990.