Background Lautropia mirabilis is a Gram-negative bacterium mainly isolated from the mouth and upper respiratory tract. To date, only two cases of peritoneal dialysis-associated peritonitis induced by Lautropia mirabilis have been globally reported: one in Australia and one in Portugal, but Lautropia mirabilis has not been cultured. Here, we report the third case of peritoneal dialysis-associated peritonitis caused by Lautropia mirabilis in the world. Furthermore, we cultivated this bacterium to improve the existing knowledge on the etiology of this condition and provide clinical guidance for its treatment. Case presentation: A 49-year-old female with renal insufficiency for more than five years was admitted to our hospital. She had been on peritoneal dialysis for six months. The patient had diarrhea and turbid peritoneal dialysis fluid for three days. With indication of infection by routine results of peritoneal dialysis fluid, mass spectrometer identification and gene sequencing of peritoneal dialysis fluid culture were subjected and revealed infection with Lautropia mirabilis. After anti-infection treatment with gentamicin and ceftazidime, the patient recovered. Conclusions Our findings suggest that Lautropia mirabilis plays an important role in the pathogenesis of peritoneal dialysis-associated peritonitis. Early diagnosis and timely antibiotic treatment may be essential for the treatment of this infection.