Peritonitis is an uncommon complication of brucellosis. Brucella peritonitis in chronic ambulatory peritoneal dialysis (CAPD) patients has not been reported before. A male patient is presented with peritonitis caused by Brucella melitensis who was on CAPD. The source of infection was thought to be unpasteurized, unsalted cheese eaten a month before the onset of symptoms. At the beginning, antibiotic therapy with doxycyline and rifampicin led to a rapid clinical improvement, with disappearance of the organism in the peritoneal fluid. However, peritonitis relapsed after discontinuation of antimicrobial therapy. Successful management required a combination of medical therapy and removal of the Tenckhoff catheter.