Bladder rupture in patients undergoing renal transplant is rare. A 26-year-old man underwent a deceased-donor renal transplant. Postoperatively, he showed a good clinical course, but after removal of the urethral catheter, he complained of pain in the lower aspect of the abdomen and in the left flank. Findings of abdominal computed tomography and retrograde cystography revealed an extraperitoneal bladder rupture. We did not identify specific causes for this condition and believe that the bladder rupture was spontaneous. However, we could not rule out the possibility of traumatic rupture by the double-J ureteral stent. We decided to manage this case conservatively, with an indwelling urethral catheter and antibiotics, instead of by surgical repair. Results of repeated serial cystography during the treatment showed decreased contrast extravasation, and cystographic findings at 6 weeks showed no leakage of contrast medium. We confirmed complete healing of the ruptured bladder and removed the urethral catheter. Since then, the patient has maintained good renal function without any complications.