72-year-old female bladder cancer patient presented with a history of ileal conduit urinary diversion; a urethral balloon catheter was inserted to control her urinary tract stoma. The patient, who reported a foul odor emanating from her urine for several days, visited our hospital as an outpatient when her urine bag developed a purple hue, although there was no change to the color of her urine. The patient's body temperature was 36.8℃, her blood pressure was 124/68 mmHg, pulse rate was 74 beats per minute (regular), and respiratory rate was 18 breaths per minute. Urinalysis revealed white blood cells, urine nitrite, and gram-negative rod bacilli in her urine. Although voided urine color was normal, urine in the bag had developed a purple hue; therefore, purple urine bag syndrome was diagnosed due to a urinary tract infection (Fig. 1). Urine color improved after treatment with oral cefaclor. Escherichia coli was also detected in the urine culture.