Spontaneous bladder rupture is an uncommon and life-threatening urological emergency, and early diagnosis is often challenging. Herein, we report a case of intraperitoneal bladder rupture in an 81-year-old male with neurogenic bladder-the case of intraperitoneal bladder rupture required late laparotomy for pelvic abscess following initial conservative treatment.An eighty-one-year-old male presented to our emergency department with deterioration of consciousness, fever, and hematuria. He denied previous trauma history and had been treated for neurogenic bladder. Physical examination revealed signs of tenderness in the abdomen. A diagnosis of bladder rupture was made based on laboratory examination indicating renal failure and radiological imaging showing urinary ascites. Conservative management with a Foley catheter and antibiotics (meropenem administered 1 g/day) was initiated. On day seven after admission, the patient complained of abdominal pain and fever, and a diagnosis of pelvic abscess based on contrast-enhanced computed tomography and septic peritonitis was made. An emergency exploratory laparotomy for peritoneal drainage was performed. The postoperative course was uneventful, and the patient was discharged on day 29 after admission.Urinary bladder rupture should always be considered as a differential diagnosis in patients presenting with free fluid in the abdomen, peritonitis, reduced urine output, and hematuria. Clinicians should be aware that secondary bacterial peritonitis can occur as a major complication of a ruptured urinary bladder.