BACKGROUND An acute necrotic fluid collection is a rare condition that occurs within four weeks of the onset of necrotizing pancreatitis. This report is of a case of spontaneous intraperitoneal rupture of an acute necrotic fluid collection that required emergency laparotomy. CASE REPORT A 61-year-old man presented with worsening symptoms following hospital discharge for necrotizing pancreatitis. On hospital admission, a computed tomography (CT) scan showed changes of pancreatic necrosis and inflammation with a peripancreatic fluid collection. On the sixth day following admission, he developed hemodynamic instability and peritonitis. Repeat CT scan showed a reduction in the size of the peripancreatic collection but free intraperitoneal fluid, consistent with intraperitoneal rupture. At exploratory laparotomy, several liters of necrotic pancreatic fluid were drained from the abdomen, followed by admission to the intensive care unit (ICU) for continued resuscitation. On postoperative day 3, he underwent open cystgastrostomy, cholecystectomy, placement of a jejunostomy tube (J-tube), and abdominal closure. He remained in the ICU for several weeks until ventilatory support could be reduced, and was transferred to the hospital ward when he was able to tolerate J-tube and oral feeding. On postoperative day 35, he was transferred to a long-term care facility. CONCLUSIONS Acute pancreatitis is usually managed conservatively, and surgical management has become less common. A case of acute necrotic fluid collection arising within the first four weeks of onset of acute necrotizing pancreatitis is presented that underwent spontaneous intraperitoneal rupture leading to ascites, peritonitis, and hemodynamic instability, requiring emergency surgical management.