Halomonas hamiltonii is Gram-negative, halophilic, motile and non-spore-forming rods. They produced cream-coloured colonies and contained Q-9 as the predominant ubiquinone and C (18 : 1)omega7c and C (16:0) as the major fatty acids. Herein, We present a case report of continuous ambulatory peritoneal dialysis (CAPD)-related peritonitis due to Halomonas hamiltonii. A 82-year-old male patient who had receiving CAPD therapy for approximately 1 year because of end-stage renal disease caused by hypertensive nephropathy presented with abdominal pain and cloudy dialysate for 2 days. The tunnel of the CAPD catheter was normal and the exit site was clear. White blood cell (WBC) count of the peritoneal fluid was 810/mm, with neutrophils predominant (60%). He was empirically started on an antibiotics regimen consisting of cefazolin and ceftazidime intraperitoneally. On the fourth day after his admission to the hospital, Gram stain of the peritoneal fluid revealed Gram-negative rod, WBC count of the peritoneal fluid was 130/mm, with neutrophils predominant (61%) and then the empirical combined antibiotic treatment was stopped and intraperitoneal ciprobay and vancomycin was started. A bacterial growing in the peritoneal fluid culture was identified as Halomonas hamiltonii. In hospital day 18, patient's clinical condition was entirely recovered and peritoneal WBC was 8/mm. Intraperitoneal treatment was continued for 21days and the patient was discharged without any problem.