Peritonitis is a common complication of peritoneal dialysis (PD) usually caused by skin-dwelling Gram-positive bacteria and Gram-negative bacteria colonizing the gut and urinary tract. Occasionally, uncommon bacteria can cause peritonitis in PD patients. We describe a case of Ralstonia mannitolilytica peritonitis in a 67-year-old woman who has been on PD for more than 10 years with no prior episodes of peritonitis. To our knowledge, this is the first reported case of Ralstonia peritonitis in the United States. She initially presented with abdominal tenderness, right flank pain, and cloudy output from her nephrostomy tube. PD fluid and urine cultures grew E. coli which responded to treatment. However, her symptoms recurred after completion of antibiotic therapy with PD fluid growing Ralstonia species. She again responded to intraperitoneal antibiotics but had recurrence of symptoms after the completion of her second course of antibiotics. PD fluid grew Ralstonia mannitolilytica resistant to the prior antibiotic regimen. The PD catheter was removed, and she was transitioned to hemodialysis. Subsequent treatment led to the resolution of her symptoms. Ralstonia species are Gram-negative bacteria that are prevalent in water supplies and can form biofilms. They have been known to cause infection particularly in neonates, immunocompromised patients, or patients in intensive care. In our patient, prior antibiotic treatment for E. coli peritonitis is likely to have contributed to the development of Ralstonia peritonitis. Clinical improvement after removal of the PD catheter revealed that seeding from the PD catheter was the likely culprit for the recurrent infections.