<i>Lautropia mirabilis</i> is a gram-negative coccoid bacterium isolated from oral and upper respiratory sites with unclear pathogenic potential. We present an exceedingly rare case of peritoneal dialysis-associated peritonitis due to <i>L. mirabilis</i> in a patient with a recent history of periodontal infection, successfully treated with intraperitoneal antibiotics. We propose that clinicians consider this organism as a potential cause of illness.