Peritonitis is still the major complication associated with peritoneal dialysis (PD). Microbacterium spp., a type of coryneform bacteria, is an environmental bacterium isolated from soil, waste water and animals. Human infection is rare, and only few cases have so far been reported in immunocompromised hosts, such as PD patients. Microbacterium paraoxydans, one type of Microbacterium spp. was identified for the first time in 2003. Only two cases of infection of Microbacterium paraoxydans have so far been reported. We herein report the first case of PD-related peritonitis caused by Microbacterium paraoxydans, which was identified by a sequence determination of the 16S rRNA gene. Based on the results of antibiotic sensitivity, the intravenous administration of erythromycin (EM) and oral administration of sulfamethoxazole/trimethoprim (ST) were selected, and PD was interrupted. EM administration was stopped after a total of 14 days. ST was administered for a total of 21 days, and later PD was resumed. Thereafter, no recurrence or relapse of peritonitis without removal of the PD catheter was observed. Microbacterium spp. exhibits multidrug resistance and such an infection is refractory in many cases. We assume that both accurate species identification and the use of antibiotic sensitivity tests are essential to effectively treat this kind of infection.