Ralstonia mannitolilytica constitutes a rare isolate in clinical specimens and to date very few infections with this Gramnegative bacillus have been reported. The first case of peritonitis in a pediatric patient due to R. mannitolilytica in the setting of peritoneal dialysis is described. It is very important to view this organism as a pathogen rather than contaminant when isolated in children with peritonitis.