A 32-year-old well-nourished man having a vesicosigmoidal fistula due to Crohn's disease received laparoscopic sigmoidectomy with partial cystectomy. The bladder wall was closed with an all-layer running suture and additional interrupted sutures using 2-0 Vicryl. Four months after surgery, the suture site on the bladder showed perforation to the abdominal cavity. Since the same event occurred again 6 months after surgery, open partial cystectomy was performed to repair the perforated site 8 months after the initial surgery. The perforated site showed a thinning bladder wall composed of normal urothelium, scar tissue and thin detrusor muscle. Non-caseating granuloma was not found in the specimen, even though it was slightly observed in the margin of the detrusor muscle resected in the initial surgery. Although it was possible that the persisting activity of Crohn's disease, subclinical impaired nutrition due to Crohn's disease or insufficient suturing of the bladder wall were involved in the bladder rupture, the definitive cause remains unknown.