A 63-year-old male patient suffered from diabetes, hypertension, and a bladder tumor. He had undergone radical cystectomy and ileal neobladder construction 1 year prior to this admission. He came to our emergency room complaining of abdominal pain after recent alcohol consumption. Muscle guarding and abdominal rebounding pain developed after conservative treatment for 1 day. The next day, emergency laparotomy for acute peritonitis revealed two small perforations in the neobladder and calculus formation within it. In addition, severe intraperitoneal adhesion was noted. After removing the neobladder stone and repairing the neobladder, a Foley catheter was inserted for urine drainage. The patient's postoperative recovery was excellent.